Yes, you have low compression pistons. If you can slow things down a bit, this is the time to rebuild the engine proper with new 10:1 pistons. I put a cam, 440source heads and headers onto a low cr 440. It did okay for what it was but the stock 7.8:1 compression pistons leave a lot of power on the table.

I wouldn't put any money into those heads. By the time you do exhaust valve seats, have the shop clean the heads and valves, and new springs for your new cam, you will be a good chunk of $ of the way to just buying a set of edelbrock rpm or 440source heads.

I ran a thermoquad and a lunati voodoo 60303 cam with 3.55 rear gears. I ran it with a stock converter but it really needed a 2800rpm converter to cover for the low-cr pistons.