I saw some earlier post that were incorrect so I thought I would pass on a bit of info.
First the 101 Axle splines are NOT the same size, they are 2mm smaller than the 115 series. 27.5 vs. 29.5 so the axles are out.
see first pic.
In the 2nd picture you will see the 101 axle at the top & a 115 at the bottom. There are 2 spacers on the 115 a thick one (original) and a smaller one. The smaller one will be used (only) These determine after assembly how far out the face of the axle sits from the brake backing plate. Very important as the shoes must be "centered" on the brake material & the drum must fit the backing plate.
As I modified 101 tubes as you can see in pic 3, I had to weld up & machine down the large flange centering flange to fit the larger (200mm) hole in the 115 housing. The lip that fit into the smaller side had to be shortened 1/4 inch as it was the correct diameter, just a bit too long. Since this has gone this far I`m waiting on another Diff I bought to get the LSD Clutch disk from and this will have a 4 disk LSD in place of the stock two.
Hopes this helps,
Richard Jemison
RJR RACING