Here is a view of the rear U-joint assembly. It is connected to the driveshaft via the flange yoke. It is bolted to the rear axle at the drive pinion flange

The front U-joint assembly connects the drive shaft and the slip yoke. The slip yoke just slides into the transmission and meshes onto the gear with it internal splines.

Use a chisel, or similar instrument, to index the flange yoke and the pinion flange. All that does, it makes a mark across those two pieces. This will assure that the drive shaft will be mounted in the same way once the repair is done.