Pupsvette76, As you have been told the heads you have are poor flowing. I know you have to have 76cc chambers to keep your compression down. Look around and try to find a set of these heads cheap. 3973487-76cc, 1.94/1.5, 3973487X-76cc, 2.02/1.6, 3932441-76cc, 1.94/1.5. You can check with a machinist to see if the 1.94/1.5 valves can be upgraded to 2.02/1.6 without problems. Get a book on porting heads so you can do this yourself. Here is an article on head porting. Do-It-Yourself Small-Block Cylinder Head Porting - Tech Article - Chevy High Performance Magazine
You can also get David Vizard's book, "How to Build and Modify Chevrolet Small-Block V-8 Cylinder Heads" You definitely need heads that breath and a large diameter (3") free flowing exhaust.