I have been studying another option for a Gear Diff. The Durango gear diffs use a 10x15x4mm bearing. I test fitted a 10x16x4mm bearing and it fit almost perfectly into the diff case. So instead of purchasing a machined bearing sleeve why not just is the proper bearing. I pulled these bearings from my SC10 4x4.

I am also planning to test fit a Caster S10B diff into the case. The ring gear is the same size so if the width fits It would be a good alternative. I have access to a pinion gear that uses a pin instead of the key but it will need to be shimmed to the shaft. I'll post photos if I get this to work. Caster Diff kits are $43 and the SC104x4 bearings are $7.29 a pair. So for about $100 for a set of Gear Diffs.