vacume gauge
find a manifold vacume source and connect the vacume gauge to there, usually if i'm not mistaken ,, there should be 2 adjusting screws in the front facing the radiator,,, I'd adjust the mixture screws where you achieve the greatest amount of vacume. I'd do one side , then the other , then go over them until you feel you have a good balance between each side. I'd turn them just slightly open ( 1/4 turn ) past the best vacume reading and see how the vehicle responds
Honestly , if it was mine , i'd think about getting a 2 barrel adapter to put a Holley 2 barrel on chevy 2 barrel intake and finding a good used Holley 2 barrel. I put a 500 Holley 2 barrel on a 327 once and it made a pretty big difference over the stocker. I had a 350 Holley 2 barrel on a 305 once and that worked good too.
Do you see any modifications in the future ??