Did all the earlier ones have valve reliefs or just 6 pack pistons? I think an earlier post said all had the same piston year to year. Feets clearly has no valve reliefs so that might be a tell tale sign of compression, I have always known/believed valve reliefs in a piston denoted "high compression" regardless (within reason of domestics) of the make.
RBs From 65 up 440-6 only, 64 down Max wedge. Same pistons year to year, no
