I have got a 1989 gta with a stock 350 tpi and i would like for it to go faster and i had a few ideas. I would like to use Edelbrock's RPM 64cc heads and on one of there tpi early head manifold base. I think i would have to get +.001 hardened pushrods but iam not sure. Then i would get a 58mm throttle body. Would i have to change my computer? Get more fuel to the engine? Etc.? If you guys think i would run in to any problems tell me and give me some better ideas or refine my thoughts.

your going to have to change cams also if you are going to swap those heads on. Ang no you do not have to change computers(ECM). You will need a new custom tuned PROM though. You can run with a stock PROM tune but you will notice a few "stuttery" spots.

you don't need a 58mm TB. Max probably 52mm on a hopped up TPI. Now that you have picked out a set of heads ...run it by a cam company to see what they can do for ya .

I picked out some 64cc heads i know my stock heads are like 60cc are something like that. Would that cause any problems? Would i have to siamese anything or machine anything down? Would i have to get those +.001 hardened pushrods and do i have to get more fuel to the engine since there is going to be more power? Does anybody else agree with d's89iroz and think i should get a 52mm tb?

keep your 48, and get a full exaust.

you do not need a larger throttle body unless you are making more than like 450-500 horsepower. the stock 48mm can handle up to that amount. And if you want harder push rods then buy whatever you want, but if your just a street motor, get stock replacements. They only way you can get more fuel is: Larger Injectors, Adjustable Fuel Pressure Regulator, and PROM tuning on the spark/fuel tables.

You do not need a 52mm throttle body just cause "it sounds bigger, looks bigger so it must make a difference." This is usually a general assumption of most people when they are first starting out. After you start outflowing the TPI runners and base, then MAYBE (doubtful) you need a larger throttle body.
Also keep in mind by increasing the volume of the heads you will be losing CR unless you have any better way of opening up the intake you may be worse off than you are. Another option that would be a little less work would be to either upgrade the exhaust (already mentioned) or bump your stock rockers to 1.6 roller rockers.

The MAF TPI system can handle the extra load. It is just top-end limited, unlike SD. It will do better with PROM fine-tuning, though.

As for the TB, don't forget that the GM crate Ram Jet 502 puts out 502 horses, and uses a 48mm TB. But, for some reason TPI will run better with a 52mm TB when combined with other mods.

Your stock heads are 64cc chambers. The RPM heads are aluminum, which requires a higher compression ratio to make the same power as iron heads, all other things being equal. So, the 64cc chamber RPM heads would represent an effective reduction in CR.

What do you mean by upgrading my exhaust( the ports, headers, what?) i do not have a cat, because i took it off. So tell me if iam correct: stay with the 48mm tb, get 1.6 roller rockers, get larger injectors, prom tuning, the rpm heads, and the manifold so i can use these heads. how much hp will you think i can get from this set up? Do i need to modify my compression ratio after all this?