If you carefully cut the housing with a dropsaw or hacksaw. Measure the amount taken out. Use that measurement of removed tube from each side and get axles cut down to suit. You only need to be accurate to 1 or 2 mm, some slack is ok. Being too long is bad.. Some axles don't have enough diameter along the full length to allow new splines to be cut. This is the worst case scenario.

If you have access to a migwelder, you can reweld the tube back together after the new splines are cut on the axles. You can get splines cut for AU$30/side, I machined the diameter down in a lathe, so all the spline dude had to do, was cut the spline.

Then get the spring perches in position.

I was lucky and only needed to shorten one axle with the open-wheeler commodore diff. I used the short axle as my new long axle, and shortened the long axle to be my new short axle. So my diff could have cost $150 total..But I payed $120 for the chrome rear cover, $150 for new disks, $40 for a cliper overhaul kit, and new pads $50, so mine was still less than $600, including the brake overhaul.

Chris