You can also convert it like Nascar did by using a bolt on slip-yoke like 4 wheel drives use then install the spline on the front of the drive shaft and standard u-joint in rear. Did this on mine before I found a 65 unit to replace it.

2003 Dodge 3500 Diesel

1964 Plymouth Savoy White 2dr sdn. 512 stroked, Dominator, New Best 9.75 @ 138.50mph
2019 Challenger Scat Pack 1320 White Knuckle-K&N Cold air filter, Billit Oil catch can, drag radials stock 11.911 @ 114mph