[ZEKE68]

I just put a 4L80E in behind a big block on stock big block mounts. Its sitting on the stock auto cross member in the back, and I have about 1 3/4" clearance between the trans and the body where the seem is. I did flatten the seem before I installed the trans just for the extra clearance, but I still would have over an inch of clearance even if I didn't. Mine is a low hump cab and there is plenty of room at the engine end of the trans. Mine gets tighter toward the tail shaft end of the trans where I have about 3/4" vertical clearance on top just before the tail shaft. V8 mounts would likely solve your issues, though it would cause you rework elsewhere.