I do not advocate using the propane torch for leak testing..PERSONAL experience..IF you hit the "spot" and the Carb spits back and dies..you have a fire on the manifold From the heavy low lying propane Gas..until it burns off..IT DOES work, but you run that risk..
Spray is safer, and if you have a good paint job and the engine is warm, shouldn't effect anything.
Fatten up your Idle jet Screws about a 1/2 turn..sounds like it's starving at random..IF you have any time on the plugs..an examination should confirm this..(clean white electrodes).
Check the fuel filter, Both at the body, and inside the Fuel inlet nipple at the Q~Jet..make sure they are clean..
AT IDLE..look at the center of the Q~Jet..they will be a "'Hole" just rear of the air cleaner stud..look down there..there will be a "Y" structure in there, that is the top of the float..use a Very small screw driver or Q~Tip, push it all the way to the bottom and hold..Fuel will rise and start to spill over the top of the carb..let it go before it dies..Do this 3 or 4 times..This will clear any crap in the needle valve.
Make sure the Mechanical advance isn't hanging up, or one of the springs hasn't fallen off...
IF the fuel is old..put some (double ) Octane boost in the tank as well as some cleaner / Water displacer.
Do a Volume / Pressure test on the Fuel pump..Because it is new does not mean it can't be dying..
Check the power brake booster for leaks..push the pedal and listen..if it roughs out and hisses..you have a problem.
Check the PCV for proper operation not stuck or sticking) AND that it is proper for the engine.