Super six set up with low comp

Compression on all 6 at 90 PSI is probably pretty good. At least it's evenly worn.
That's a good sign. I like a good distributor re curve better than the super six swap.

The super six swap always results in poorer mileage. Since both barrels on the carburetor open simultaneously, it drinks more gas than a one barrel. Now, go for something progressive like a weber and that changes. Of course it's also more money.

If you really want to make a big difference on a stock engine, get a timing set with multiple keyways and advance the cam 4-6 degrees, then re curve the distributor. It will make a world of difference. Then that bigger exhaust pipe will pay off.