you did use the block plate between the block and bellhousing didn't you? I have seen people not put that in, and it acts as a spacer. Also I am not 100% sure on this but if I remember correctly the 390 flywheel does work but you have to put a spacer behind it as I don't believe it's set quit as deep as the 460 flywheel, but thats something someone else hopefully remembers better than me, it's been a long time since I messed with that swap (as in about 25 yrs.)