I have a '50 3600 and swapped out my rear axle. The rear axle on the 3600 is considerably wider than the 3100 models.
This was a perfect fit, as far as width. I used new U-bolts and a heavy duty spring plate- reversed the plate so that it rides on top of the axle. Heavy duty 2 inch wide spring perches, spring plates & shock mounts are available at Ruffstuff Specialties that will fit this axle.
1999 S-10 Blazer ZR-2 It's 5-lug, GM metric. It must be a "ZR-2" for proper width.
It is the correct width, has disc brakes, an 8.5/8.6 inch ring gear and all ZR-2's were 3.73:1 with the G-80 locker. I removed my locker, as I think the G-80 unit is too troublesome.
There are a few pics of my installation in my link below. I have no idea what you might use as a front axle, but am wondering whether the front axle from the same truck would be a good fit?
