If I was to do a rear steer I would use the front axle assembly.
Roll the whole thing upside down to correct the gear rotation.
Weld in a new bunge for oil filling
Grind the ball ends loose and rotate 180 deg and reassemble.
The leaf spring mounts will be set up for spring over.
No fancy parts just work out your rear steering control and youre about done.
An added bonus is that the pinion would be on the high side of the case giving you better clearance.