I have two W50 gear boxes for sale, one from a 79 RA 40 the other from a 81 RA 40, 81 one needs the selector fixed, the other condition unknown, $150 each, Plus I have a complete diff from the 79 $150 ono.
the diff is a bit wider then a KE30 diff and it is four bar link not leaf spring mount. I had a 1000-dato with a late model diff under it, we run front wheel drive wheels on the car to fit under the guards. If you still want it it will fit you RA23 it yours with Kamac srings and shocks for $75.