Your '76 carb set should have vacuum ports on the sides of the carbs capped off by large flat head screws. You can install nipples for the gauge hoses temporarily to do a sync. The thread size is a standard M6 x 1 .....
Many "gut" some M6 grease zirks (drill end until ball and spring pop out) and use those.
Many "gut" some M6 grease zirks (drill end until ball and spring pop out) and use those.