Rebuild matching number 350 or replace?

Hello. I'm restoring a 70 lemans sport convertible for a weekend driver. It has the original matching number 350 2BBl engine. Debating if I should have the original engine rebuilt or replace it with a 400cu. Does a matching number engine in a lemans convertible make that much of a difference in the value of the car?
Aslo rebuilt prices on a pontiac are crazy! Best quote so far is $5100 pulled and reinstalled.
Appreciate anyones thoughts.  

If it is a true pontiac 350 then I would stay with the original engine.
Are you rebuilding it back to stock or are you building it up for more power.  
professional hi-performance engine builder

Horsepower sells engines and torque wins races

Also check out northernautoparts.com for rebuild kits they usually have the cheapest prices on there kits.  
professional hi-performance engine builder

Horsepower sells engines and torque wins races

If I keep the original engine will likely build it back to stock and just have it bored over and add an edlebrock carb  

Ya I would keep the original 350.
What was the price to just rebuild the engine with out removal and installation.  
professional hi-performance engine builder

Horsepower sells engines and torque wins races

The price includes pulling it rebuilding and reinstalling.  

I think the numbers matching factor on a 70 Lemans Sport would depend if the engine option was a rare one, like if it was ordered with a 455HO or 400 RA III (not sure if either was even available with the Lemans Sport). I would just store the 350 and put whatever size engine you want in there, since a 350 won't make it more valuable.

The prices you are getting for an engine to be removed, rebuilt, and installed aren't too out of line with what most professional garages would charge- custom and restoration shops will likely charge even more due to the manhour-intensive detail work that is required to do a complete engine/ engine bay restoration. I rebuilt a 389 for a customer with a restored '65 GTO, and the total for the engine rebuild and install was about $4900 (including a $500 389 replacement block and crank). I'm sure you could find someone to do it cheaper, but you get what you pay for- the last thing you need is some hack mechanic ruining your car. Pay for a known Pontiac builder who can give you references- it will cost more than some generic mechanic or garage but in the end you will get your money's worth.

Geno  

It used to be that matching numbers cars was a big deal. not so much any more. unless you have a very rare car such as a 70 hemi cuda or the likes, it wont make a lot of difference. In fact, it may help. Some clone cars are selling for nearly as much as the real thing. Have fun with the car and do what you want with it. keep the original parts and you can allways put it back.  

TAKE THE ORIGINAL OUT. IT WILL BE WORTH SAVING FOR POSSIBLE FUTURE SALE OR RE-BUILD
CHECK OUT A 400,455 FROM ANY NUMBER OF COMPANIES-HAVE FUN WITH A DECENT AMOUNT OF POWER 400- 6X HEADS, RA IV CAM,HEADERS ,HOLLEY 331O,PERF.INTAKE  375-400 HP
EVEN MORE FUN A 400,455 W/EDELBROCK HEADS,PERF RPM,750 EDELBROCK CARB,HOOKER HEADRS

THE ABOVE MENTIONED PACKAGES ARE PROVEN AND WORTH THE MONEY  

While the 350, 2bbl Lemans Sport may not be a super collectible, I think there is a niche for mainstream cars like it. Definitely keep the original motor so it can be put back in, or rebuild it stock or slightly modified and experience what that car was all about when it was new. If you aren't a racer, you maybe don't need a RA4 400/4spd/3.91 gears. The car will definitely be more enjoyable for cruising with the stock setup and the mileage will be far better as well.
Maybe the best bang for your buck is to rebuild the bottom end to stock specs, add a slightly hotter factory cam (067 or 068), 3-angle valve job, stock 4bbl carb and intake from a 1970 400 (or an Edelbrock Performer and 600cfm carb of your choice) and a factory style 2" or 2 1/4" dual exhaust with manifolds for a little more get-up-and-go without a huge outlay of cash and the hassles that go with big power and low gears. This last option is probably the way I'd go, it's easy enough to swap back to a stock cam and intake if you want to go concours.
Steve  
A little help... 'cause we don't all have to learn the hard way!

Barney is right on! I would go the 067 cam and a nice 4-barrel set up. Not to spendy and can be swaped back in a couple of hours if the sale price dictates so. I would bet any buyer would be happy with the 4-barrel set up as long as they had the original in the trunk upon purchase.