Just ante up for a Quaiffe, they're only about $1200.

We had 2 LSD units that we swapped between about 4 gearsets. I think we eventually sold one of them and then just swapped it into whatever diff we were running that weekend. PITA but once you set each one up you can swap the LSD unit around pretty quickly. I think the last one we bought was about that much money 10 years ago.

Subaru's use R160's, and might use R180's. Can't remember. Riley proly already told you what to look for in the junkyards. Good luck. Oh, and don't go nuts on the preload. When you find one I'll tell you the hot tip.