7 1/4 Rear End clean up/gasket questions

You said it " vent cap " Make sure that it is loose and not clogged or you will get seal leaks elsewhere. Work similar to the old road pipe. It allows pressure to vent to the atmosphere. Just high temp silicone to seal the diff cover.
AXLE, REAR W/DIFFERENTIAL AND CARRIER CHRYSLER 7 1/4 N-1