I don't have heat issues. My car has only heated up once, never overheated. The heat was all from the TH400 trans, which when left in drive at 0 - 5 mph for a couple of hours in 90+ degree weather, does not have much opportunity to cool.

There is something else at play here. I will have to tear it down to find out what.

Does anyone have compression height figures for the common replacement piston forgings and for factory pistons?

Different machine operators on the assembly line? I don't think that the cars were plagued with detonation when new.

Yes, the cast pistons made for aftermarket were (and are) junk. Those measurements don't surprise me. What I'd like to have seen is what the below-deck measurement was after swapping the pistons.