Hey There,
I realize this post is going on two years old, but in case some one perusing the sight wanders to it to pick up some info, that is why Im post a reply now anyway.
I had the same issue with an 82 SX4. Snapped the rear inner shaft at the hub..... :-P Locating a 27 spline set up was virtually impossible. The prices for similar replacements in model 20 rear was about $400 bucks. For JUST the axle and hub! I researched and found the best bang for the buck (and a bit more work, but WORTH IT). Get rid of the AMC Model 15 rear (cousin of the D35C)! An entire Jeep XJ Cherokee Chrysler 8.25 or D44 rea differential will swap in. They are way more stout and parts readily avalible for servicing. I got a 8.25 rear from a 92 for $150. They are all over. D44's harder to find. The diff I got was open, so I put a lock-right in it while it was on the bench. New outter bearings and seals as well just because.
The install: You do need to switch the shock mounts around, and reverse the brakeline orientation so the brass union lines up. The yolk is the same size as the AMC drive shaft u-joints.....you just need to either get a Cherokee U-joint or take off the inner clips on the yolk caps.
The XJ axles are also larger diameter (3") and you'll need new U-bolts and spring plates. That will sit the car up in the rear an extra inch too :-). Wheel bolt pattern and width are the same as the AMC.
All in all, I am super happy with the stronger axle and lower gears it came with (need to change the front). The locker is an awesome addition as well. I did a 229 T-Case conversion last year, and ran the Eagle over Black Bear Pass in Colorado. It was SWEET! So I am stoked for the front to be regeared, have low range, a locker and mild lift, with that Chrysler 8.25 rear. [[Im not so worried about the c-clips because of the way the lock-right encapsulates them when assembled. ]]]
The AMC rear axles are a known weak point and this is an awesome fix!
I still have the remains of the old axle with 2.72 gears near Denver if anyone needs it.