Vacuum on 1968 GTS 340 4 spd.

I'll re-check the numbers for you. In fact, I'll post and PM the worksheet info.
Same Pin 132 weight as the 030?

Can you show me your calculation? So far I,ve found
Stock STD 340 Pistons 719/Pin 154
KB243-020 Piston 597 but can't find pin weight.(My pistons)
KB243-030 585 /132 (Not mine)