318 +.030 Dieseling

I'm out.... Last volley

Last time, set the timing at idle to 18 degrees BTDC. See how it runs. Reset idle speed and readjust the mixture screws.. I bet your big RPM drop into gear disappears. If not you have a likely vacuum leak somewhere. Those carbs are notorious for having linkage interference with intakes, especially on the pass side. Look for fuel dripping in from the boosters as well, another bad issue from too high fuel pressure.

Keep revving it up until it stops advancing to verify the mechanical advance in your distributor. Could be 4K+ for RPM. If it's got 22* mechanical, you are WAY short from my math. LOL

DO NOT connect the vacuum canister to ANYTHING when doing this. IGNORE THAT POS CAN FOR NOW!