I have a friend that put a 6.0 in front of an old 4 speed in an 82 3/4 4x4 that hes using as a pulling truck. When he first put it in he used a stock 5.3 flywheel. I'm not sure if he used a spacer or anything on the flywheel. I do know he did end up buying an aftermarket flywheel from pace perfomance that was made for the swap.