Originally Posted by 18camaro
it has a .525 lifter cam. 1 5/8" headers with 2.5" exhaust. its a th350 3 speed tranny built and has a shift kit. and it has a 308 rear end. the block is not old he said the safest guess would be 50000 on the lower end but more than likely less (the guy he bought it from swap out the 6 and put in the v8)
Whoa Kay, alright this has been breathed on, not just some 305 with a big carb. So do you have a clue as to what heads are on it? Casting numbers are under the valve covers. Knowing the pistons would also be good as many are dished for compression ratio relief. Flat tops with 76cc or even 64ish cc heads work well from moderately high with the former and high with the latter chamber. Dish pistons come in two types, circular not the best for detonation resistance and "D" dish which is better because it puts the dish under the valve pocket and places a flat surface like the flat top piston against the squish/quench deck of the head which is good for detonation resistance and efficiency.
Pick up a copy of the December issue of Chevy High Performance, they have a back to back test of 882's I think against some aluminums which might be an AFR, they don't have Dec's on line yet so I'm having to feed off my geriatric memory on this from sittin' on the throne a couple days ago reading the article. How's that for TMI?
Anyway the modern fastburn aluminum head was good for about a 40 hp peak over the older cast iron. This is pretty consistent between older heads from the SMOG era back to the beginning of SBCs with modern heads whether aluminum or iron. So iron vortec to aluminum fastburn type heads (typically with a heart or kidney shaped combustion chamber that features the spark plug toward the ex. valve and against the chamber roof, chamber crowds the ex. valve on the sparkplug side and is relieved around the intake on that side with a beak between the valves is what you're looking for) whether from GMPP or an aftermarket source like the AFRs should pump up the action.
The automatic and 3.08 out back aren't the best combo with your cam, the bigger heads won't help that either. The power band is just going further up the rev range. You can deal with that when you get there. A built 700R4 would make a good choice with a 3.5 rear, that would get the revs up in 1,2,3 and give you a nice OD for cruising the interstates.