The NV 4500 will not directly swap into the earlier truck. The bellhousing bolt pattern is different (wider) as well as having the larger bearing retainer. To my knowlege, no one makes a bellhousing with the correct bolt pattern and index bore to fit that trans to either the Chevrolet or GMC inline 6 engines. Advance Adapters does make them for the later 6 and V8 engines, but I don't think they have any with the bellhousing engine mounts used on the older trucks. If someone was to step up and manufacture such a bellhousing, though, that trans would be an exellent option, especially for the guys with 3/4 and 1 ton trucks that need the extra strength.
