I think that any '71 or later GM K10 front axle assembly would switch into your '64. You most likely would have to change the steering gear assembly which would require adding a PS pump to the engine.
Many years ago my brother in-law had a general store in the Truckee NV area, he had a '64 -65 K10 4x4 that had a snow plow on it to clear the parking lot. The manual steering was a bear to drive, especially with the plow. A late model front end assembly with PS, disk brakes and open carden joints was installed under the truck, driving problem was solved, my brother in-law used the truck for years, many in the winter so he hardly ever took the chains off. Wm.
