i do want around 450-500 horses, just saying i heard threw several people you can get 400 horses or so with the right stock parts.  

i have two pairs of chevy heads one came off the 70' 350 and the other came off the 85' 305. is either one of these heads worth rebuilding to obtain the 450-500 mark?  the 70' 350 heads are 1.72/1.50 valves don't know the combustion camber size.  the 85' 305 heads are 1.84/1.5 valves, 58cc chambers.  will these 305 even fit? if so will it have too much combustion? i will like them to last, reather be safe than sorry. what kind of valves should i go with?  i got that edelbrock rpm intake,headers,ign. i know its best to try and get them to complment each other. what kind of ratio will these heads give me using forged flate top pistons?

Neither of these heads are suitable in a modern engine. By the time you rebuild them you'll have as much or more money in them than a new set of Vortecs. The Vortecs are worth 40 or more horsepower over ported camel hump heads and far more than that over SMOG heads of the 70s and 80s.

I wouldn't run a forged piston in a street engine, they just require too much care and feeding. They must run a wide clearance which results in a lot of skirt slap till the engine get fully warmed. Everytime you stop at Jack In The Box and let the engine cool down, you have to go through the warm up routine again. It's just a big pain, if not running laughing gas or a blower it a pain you'll find you can live without.

Pump gas requires that you stay around 9 maybe 9.5 with a Vortec style cast iron head. Aluminum can run a half to a full ratio higher. The Vortec hits around 64 cc chambers. The equation to solve static compression is (cylinder volume + chamber volume + piston crown to block deck clearance + gasket volume +or- piston dish or dome volume) divided by (chamber volume + piston crown to block deck clearance + gasket volume +or- piston dish or dome volume). Chevrolet adjusts compression piston dish volume, but production pistons till the new LS family of engines used a simple circular dish. This is not a good mechanical design from the stand point of detonation tolerance. A "D" dish or flat top piston is much better. With this design the flat section of the piston closes closely with the flat surface of the combustion chamber forming a tight squish and quench surface that builds a lot of "mechanical" octane into the engine, greatly improving its resistance to detonation and pre ignition. This closing of the flat surfaces really needs to be at least .080 inch and is much, much better if held at .040 inch. You really need to have your engine apart to measure piston crown to deck clearance and combustion chamber volume before doing much of anything. With those values you can backwards compute what the gasket thickness and piston dish (if any) volumes need to be to arrive at the proper static compression ratio. Remember that longer cams require more static compression, consult with your cam grinder on this if your getting over 220 degrees measured at .050 inch lift.  For a street piston I'd go with a cast hypereutectic with an engine that sees the occasional high RPM blast. Forged if high power and high revs will be sustained for minutes rather than seconds or if using a power adder.

Bogie