there are two that i am aware of. the difference is the large transmission input shaft hole where the tranny bolts to has two sizes. (example) the sm420 uses the smaller sized hole, the larger hole works w/ sm465's and T5's. I believe the difference is about a 1/4'' dia.

all later years of bell housings (same engine bolt pattern) will fit on an L6 &/or V8

Jim & Caroline
The highway is for gamblers, better use your good sense."
Gooday-that's my 1¢ answer due to the lousy economy ~ cause I ain't got - no . mo . doe
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