To attach a GM 4500 to a 465 or 420 bellhousing, just make the retainer fit by boring out the bellhousing, making a spacer, turning down the retainer, or some combination. Mount the trans. up to the bellhousing off the engine, mark the existing bellhousing holes in the 4500 trans., drill and tap the new mounting holes in the front of the trans., make the bottom ones blind, or seal them up so you don't get a bath every time they are removed. If using a bellhousing w/o a bottom access hole, must mount the trans to the bellhousing before the engine.
Ed, if I understand your post, you are saying an sm420 bellhousing can be bored and redrilled to mount an NV4500 directly to it without an adapter plate. I'm not sure I agree or disagree with you. First generation chevy NV4500 transmissions have a 5.125 inch bearing retainer, and a mounting pattern that is unique to 1993-1995 chevy NV4500. This incarnation may work in the mannor you described. The rest of the NV4500 transmissions have a bearing retainer that is 5.60 inches. Cutting that much off a sm420 bell will put you close to the center of the clutch ball mount. The bearing retainer of an sm420 is 4.686 inches. Just something to consider. If you have mounted an NV4500 directly to a sm420 or sm465 bellhousing, I for one would definetely want details of what was done. The AA adapter plate costs around $300, and still needs machining to go on an sm420 bellhousing. I am open to new ideas.
Nick,
I'm still trying to find those pics in my hard drive
John
