Is it possible to change out low compression pistons and replace them with higher compression ones?What's all involved in doing this and do you have to rebuild the whole engine?The engine only has about 8000 miles on it.

 

No need to touch the block or pistons. You can get higher SCR by milling heads, thinner gaskets or small chambers.
Could you be a little more specific? What size pistons are in there?

 

Also what are your goals, n/a will work better with higher SCR's but FI loves the lower numbers. 9.1:1 works well with a supercharger and maybe a tad lower for more wild turbo setups.

 

its 9 5 to 1 compression with ported 6.0 heads.im removing the procharger and i heard by it being lower compression it will have below stock hp.

 

That is true, 1:1 compression is worth about 3-4% difference. If you want to get the compression up, get some small-chambered heads, something like a 5.3 head, have them ported, some thinner head gaskets, and call it done, you'll have good compression then for NA.

 

The "as cast" Dart 205's have a 62cc chamber which combined with the right head gasket should raise your compression enough for your needs, keep the bottom end stock and put money into heads/cam.

 

why r u removing the supercharger?

 

the front mount intercooler is blocking air to the radiator and causing the car to overheat at idle

 

Relocate intercooler and/or get a higher capacity radiator.
Your issue is your intercooler location. There should be minimum 3>4 inches between them if radiator doesn't get straight air.

Is this a Z or Firebird?

With a Z just relocate the cooler forward, just behind front plate area, cut that area out and use a billet or mesh to cover.
The best I've seen here just uses a fibreglass cover and removes all the stuff in front of radiator for straight air.