Need some help upgrading my drivetrain.  I have a '77 GP w/Pontiac 301, auto. trans.  Would like to bump to a 354cid Pontiac and a modern tranny w/O.D.  Need to get a LOT better mileage and it has to be as low-buck as possible.

Thanks,
Jeff  

Well what kind of power are you looking for.  

Pontiacman8:
Well what kind of power are you looking for.

Actually, I have a thought on what I'd like to hear about...  Take a 400, use a 301 crank and longer rods for higher rpm, but that's a money build I don't have the bucks for, so something with a 4Bbl carb, mild cam, decent dual exhaust...  Need a gas-mileage engine, not a race beast.  Later, would like to switch to a Holley 4 Bbl fuel injection system, for better management.

Maybe use a Chevy pickup 6 speed and re-gear the rear end to something like 2.70:1, which puts the 1st gear equivalent to around 4.10:1...  BUT it passes 1:1 in 5th gear, so that gives 6th as 'overdrive' and keeps it at a better operating rpm.  

Actually, I bought it in Philly and drove it to Texas, then, while putting new plugs and wires and new rotor and cap in, I got two wires bass-ackwards and blew the thing up.  Backfire was so loud my son thought I'd blown the entire car up.  Muffler is trash and now she won't start, so I figure to upgrade in one jump...  

Well you might not need a pontiac 350 for the power you might want would 250 H.P. be good...  

Used to have one('77 GP w/354, auto), while in the Army.  Got better mileage.  354 makes more torque at lower rpm than the 301, allows better gearing for mileage would be my best guess.

Worst mistake was taking it to Germany and selling it.  MP's clocked it at 124 mph and gaining, on an on ramp to the Autobahn.  Sold it to another GI...