shortening 8 3/4 truck axles?

I did this in 2002 with my 72 swinger. Narrowed a truck rear end (8 3/4) to 49" and mini tub the car. Moser does a process called cold splining. The axle is already hardened. It was $95 and shipping was almost as high both ways. A friend did the same thing in his race car. Not such a good idea. Hard hitting big block and a little nos. The axle splines looked like a barber shop pole. I would buy some from Dr Diff. I never had any issues in my car and I started with a 360 and went to a 440 that was about the same as a 69 hp motor. The point is, street ok, race not so ok. Russ