318 Engine stumble

Can you post pix? It would be good to see the nubs on the distributor cam. It sounds like the are worn. The coil won't get a good charge each cycle with too small of a dwell.

BTW, on the ballast, checking the resistance value is wise. There a quite a different number of ballasts and most are wrong for the Mopar system, points or electronic. It uses lower resistance values for the coil and ballast resistance than many other systems.

For the blades having a leak, I assume you mean by the throttle shafts. That usually makes the idle speed erratic. But you can spray something mildly combustible on the shafts on the outside and see if the idle speed jumps up.