360 engine vibration

Was also wondering about cam timing. Suppose no way to check other than removing cover. Then again what cam is in it?? ? Looking down the dizzy drive hole the cam has a green painted band near the dizzy drive And looks newer Cleaner then rest of engine top of piston are quite carboned up and look original. Because the engine is externally clean I thought it was a recent crate engine but I'm wrong with this. The heads must have been off as the valve springs are clean unlike the rocker shafts. When I replaced the Crank seal the lower cam sprocket is after market. With s359 and the chain is clean. Maybe someone swapped the cam?