On the Dodge and International, as well as some Ford products, the transfer case was mounted separately from the transmission, very similar to how the stock transfer case is in the '66 and earlier 4x4s. The later GMs have the transfer case mounted directly to the transmission with an adapter. The SM420 was never used with an integrated transfer case from the factory, however, I do believe that Advanced Adapters might make one for it. The later 4 speed trucks generally used the SM465, which has a synchronized first gear. It also has a slightly larger front bearing retainer, which would require either milling the retainer or the index bore of the bellhousing to work with the stock bellhousing in a 65. Some trucks from the early '80s also used the MY6 4 speed, which has an overdrive 4th gear. I can't say for sure about the bolt pattern or the retainer size, as I've never really messed with those all that much.
