As far as the heads and cam go, 455s with 6X heads and 041 cam is a pretty popular combo. The 9.7:1 compression ratio you mentioned would be about perfect. Big car with 3.08 gears might be a tad much, I’d guess you’d wanna run Rhoads lifters.
One thing about your 6X heads, sounds like they have OEM valves, generally highly recommended to replace them. Factory valves are 2 piece, with the head welded to the stem. Lot of horror stories about a head popping off and killing an engine.
Seems like you have a good package going together. Here’s a piston option for not much more than the KB hypers:
https://butlerperformance.com/i-2462...tegory:1234832