Best way to build a 68 Pontiac 400

any suggestions?? cam? heads?  i was going to go for a set of ram air 3 heads and a comp cam.  

What is the intended use?
How much power are you trying to get out of the 400?  
professional hi-performance engine builder

Horsepower sells engines and torque wins races

its just a street car trying to make it go fast around 400 horses  

What heads are on it now.  
professional hi-performance engine builder

Horsepower sells engines and torque wins races

THE EASIEST WAY IF YOU HAVE THE FUNDS ARE TO INVEST IN EDELBROCK HEADS
NO MATTER WHAT YOU DO TO A SET  OF SOCKERS YOU STILL HAVE A HEAD THAT IS BY CURRENT STANDARDS  ANTIQUATED  NUMBERS MATCHING RE-BUILD YES PERFORMANCE MORE BANG FOR YOUR BUCK AND SUPERIOR FLOW NUMBERS-JUST DO THE MATH AND YOU WILL BW WITHIN A FEW HUNDRED DOLLARS OF AFERMARKETS MOST OF THE TIME  

EXCUSE MY SPELLING GENTS
THE EDELBROCKS  ARE ROUND PORTS RAIV STYLE WHICH WILL GIVE YOU 400 PLUS WITH A CAREFULLY SPEC'D CAMMOTION BUMPSTICK-NO OFF THE SHELF CAMS PLEASE   I HEARD WALMART WAS GOING TO START SELLING CAMS  

its got 99 heads the ones with smaller valves thats why i was going to get the ram air 3s caues they have 2.11 heads  

IF YOU ARE DEAD SET ON USING STOCK HEADS THEN REMEMBER A VALVE SIZE INCREASE   DOES NOT NECESSARILY INCREASE HP BUT OFTEN TIMES TORQUE THE RPM RANGE IS CRITICAL
USE THE RAM AIR 4 CAM AND IF YOU HAVE AN AUTOMATIC A VAC SEC CARB  DO THE PRICE CHECK YOU MAY BE SURPRISED (EDELBROCKS)LESS WEIGHT TOO.  

Don't necessarily jump at aluminum heads, to begin with basic metallurgy tells us that aluminum is not thermally efficient and pulls alot of heat out of the combustion chamber. That's fine if you are running on the ragged edge of too high compression ratio and not enough octane, but a well thought out combo with factory iron heads will make plenty of power too. When you factor in the $2000+ price tag for a set of Edelbrocks and even more for others, the iron heads look like a pretty good deal. Any of the late 60's, early 70's small chamber heads with 2.11 valves will meet your performance goals will little more than a stock rebuild and stay away from the ra4 cam, guys have been messing with that combo for years and unless you have the round port heads it loses power.  
Trying to help... 'cause we don't all have to learn the hard way!

The ram air 3 heads are great heads especially if you have a good port job done on them I would recommend getting a set but to run pump gas you will have to use dish top pistons or have the combustion chamber opened up from 72CC to 80-82CC and flat tops will yield a 9.2-9.5:1CR.  
professional hi-performance engine builder

Horsepower sells engines and torque wins races

http://store.summitracing.com/partdetail.asp?part=LUN-00071LK&view=1&N=700+150+4294840135+    would this be a good cam?  

and with my new block it comes with forged pistons instead of cast and a windage tray would that make more power than cast pistons and no tray?  

Forged pistons (assuming the same design and compression height) will not make any more power than cast pistons. They will however take more pounding than cast ones, especially if you choose to run nitrous. Depending on piston weight, you could also lose a small amount of power pushing heavier pistons around. Piston choice really needs to be based on the whole package, although forged are generally the way to go.
The same goes for the windage tray, horsepower and torque are only affected by oil windage at the upper end of the rev range. The real purpose of the windage tray is oil control.Trying to keep oil from whipping around and being stirred into foam and returning it to the pan to supply the pump is the real goal, any gained hp is a bonus.
I've been reading through this thread and although you've asked for cam and head advice, you haven't given any info about the car besides it being a street driven car that you want 400hp from. What any knowledgable engine guy needs to know before making recommendations is stuff like car model and weight, rear gearing and tire sizes, auto or manual trans/ torque converter stall speed, available octane rating of fuel, street car or street/strip, highway cruiser or around town stoplight brawler and so on. It seems today that everyone wants the magic 400hp because that's what Hot Rod magazine is pushing down everyone's throats as a "basic street engine", usually a stroker small block Chevy. Our Pontiacs don't need 400hp to turn low 14's or high 13's in the 1/4 mile, we get it done with big torque and mild gears.  Answer these questions and we can help you make a better, well informed choice. If I had a dollar for every guy who asked for 400hp and then hated living with the beast when it was done, I could afford to build one for myself!
Steve  
Trying to help... 'cause we don't all have to learn the hard way!

its an 81 trans am so its not a heavy car but not a light car i would say around 3000 pounds but im not sure rear end is stock so id say 373 it has big tires on the back wider than normal but not slicks. its a auto trany thats only a 350 so its underpowered thats the next thing i will break... no stall i want to run 92 octane but i can run non oxyinated premium every once in a while.  its going to be a street car light brawler im not looking for a cruiser.  and ive already got my new motor its a 74 pontiac 400 that im re building caues its really gunked up.  its stock bore and im going to keep it that way so i can have more motor strength and when i decide to rebuild it again i can bore it after 100000 miles or when ever.  and with that i got a set of #13 heads witch he told me are ram air 3 but i dont think they are but they have the 2.11 valves so its basicly the same. they are 1970 i think. and im going to get a cam but i dont know what to get for around 100-200 bucks that wont push my valves into my pistons.  

Rusty,
Here's a perfect example of why I ask the questions I do. A 1981 TA weighs between 3700 and 4000 lbs depending on options, A/C, power windows, full size or spacesaver spare, aluminum or steel wheels all add up to a heavy car especially with a Pontiac V8 underhood. My 79 no-option Formula with Rally II wheels 75 Pontiac 350 and TH400 trans weighs 3680lbs with a half tank of fuel and no driver/passengers or spare tire. I think your TA weighs more than 3000! Next is the gear ratio, in 1981 the lowest gear available was 3.08:1 with 2.41, 2.56 and 2.73 much more common. Being a th350 is not a problem, if the car was originally 301 powered or has the dual pattern bellhousing you can have the th350 built to handle the power. Installing a th400 requires a shorter driveshaft, different slip yoke and moving the crossmember.
Back to the engine, if it really is "gunked up" now is the time to do it right not throw a bandaid on it. Why the worry about weakening the block? The 400 can take the standard .030" overbore without weakening it and if you look after the engine it will last for way over 100000 miles and it will make more power with round straight bores and new pistons.
My advice to you is to have your 400 bored and squared by a competent machine shop and install new dished pistons to lower the compression ratio with your #13 heads. Rebuild the heads with new valves and springs (to match the cam). Add an Edelbrock Performer intake and 750cfm carb or a Performer RPM if we determine you have the gears (and therefore the cam) for it. 3.08 gears will work great with this combo if cammed properly or change to 3.42 for more stoplight action. But first find out what gears you have and the actual tire size you are running and then we'll pick a cam that brings it all together. Remember 300 real world hp is nothing to be ashamed of and the torque will blow your mind, this isn't a "no torque/6000rpm small block chevy" we're dealing with, it's a Pontiac 400 and we make torque...lot's of it!
Steve  
Trying to help... 'cause we don't all have to learn the hard way!