Looks like it might be a pretty decent car. Sounds like a good plan for the 71, too.

A couple of possible low cost upgrades for 305 heads. Chevy put some decent heads (I know that's an oxymoron when you're talking about a 305) on the 4 barrel 305 truck engines in the mid 80's. I don't remember the casting numbers off the top of my head, but I have a set of them out in the shop. I can check them out and get the numbers if you want. They had 55-58 cc heart shaped chambers. The local stock class dirt guys used them on 350's when they were limited to stock parts and claim rules.

Also, the Corvette aluminum heads had smaller 58 cc chambers and most likely flow better than the parts you have now. Milling would bump the compression a little. The ZZ crate motors used similar heads with a standard old style intake bolt pattern.

I built a 305 for my son's truck and used flat top pistons, the "good" truck heads that I pocket ported, a cam from Summit that was similar to a 300 HP 327, Performer RPM manifold and a 500 cfm Edelbrock carb. I also recurved the HEI distributor. With headers and good exhaust, that engine ran much better than you would think and still got decent mileage. He wanted a 350, but the 305 and the intake was donated to him by a good family friend. After he got out on his own, he appreciated the economy of the little 305.