64 3 sp to 77 4/OD Installation

A 64 has a trunnion type drive shaft and a 77 trans obviously has the slip spline style. Unless you have a matching driveshaft that will be a problem.

It clears the t-bar/trans mount crossmember Ok.

You need the OD clutch fork that matches the OD bellhousing. You need the OD bell as the trans bolt pattern is different than the early 3 speed trans.

The rubber mount should bolt to the trsns mount no problem.