What size carburetor should I be using LA 360 engine?

Quick and easy;
Assuming the fuel is fresh, the fuel level in the bowl is correct and stable, the secondaries are closed up tight, the PCV is correctly plumbed, and the Distributor advance springs are both in there and working;
Defeat the Vacuum advance.
Reset the Idle-Timing to 8*,
set the mixture screws to 1 turn,
and idle it up until it quits stalling when going into gear.
There's a start.