I got this done for my diff. I had to go to two different places. Berry Racecars in Upper Hutt to shorten the casing and move the mounts. That was $100 four years ago.
They sent me to Whakatiki engineering to shorten the half shafts. This was the expensive bit, might have been as much as $200 per shaft(it was a long time ago). But they had the equipment to cut splines on a shaft. Apparently there are two methods of cutting the splines.
Heat the shaft to remove the temper(hardening) where you are going to cut the splines and re-temper it when its all done. I think this is harder but it saves the cutting bit thing.
Or the method they used on mine. Cut the splines without removing the temper, this method is easier but it is destructive on the (expensive)cutting bits. Hence the cost. But there is no chance of $$% up the re-tempering of the shaft(and bending it).
Someone correct me if this is wrong and I was fed poos and wees.
Another note....I think I might have had an st141 diff.....maybe. They couldnt shorten the original half shafts. The shaft got narrower just after the spline then got thick again so there was no metal right where the new spline needed to be cut
I ended up at pick a part pulling out all the rwd halfshafts till I found one with a bigger diameter spline/shaft and the same size bearing that they could use. Might have been a corona wagon....it had leaf springs, I wasnt paying attention to the cars, just the axles.
I removed 25mm from each side.
Irrelevant information. YAY!!
BTW: Overkill is too HEAVY! WTF does a hilux axle WEIGH?!