Timing Dance ! Vacume Advance ?

If your timing dances around with the vacuum advance hooked up then I think you should try re-phasing the toothed magnetic rotor in your distributor. If you look it should have two slots to fit on the dist. shaft pin located roughly 180* from each other; they are actually about 170-175* apart and depending on the one you slip over the pin your rotor-to-cap phasing will be off. This causes the distributor rotor to be too far away from the cap contacts when the distributor is at FULL advance (mechanical+vacuum) and makes the engine misfire at very light throttle.

You know I just looked up the part number for your carb and it is the 800 cfm version; this carb is TOO BIG for your 360, plain and simple. Swap a 650 cfm Performer on there and it will run much better.