I noticed this info is about 10 years old now, and doesnt cover the Subaru R160 VLSDs that came in WRX and Outbacks and others from '99 and up.
Any subaru legacy outback with cold weather package from 99 to 03 will have VLSD R160, and any Outback from 01-03 will have the VLSD as STANDARD equipment. Look for the heated windshield wipers and heated seats to know if the car has cold weather package. These cars are now over 10 years old and very easy to find. I found three R160 VLSD equipped outbacks in the Ecology just this weekend.
They are available in 4.11 for the manual transmission outbacks and a nice zippy 4.44 in the automatics.
In '99 Subaru changed their VLSD design to no longer require the longer extra set of splines on one axle to engage it.
This means all you have to do is have some c-clip gooves machined into the end of your factory Datsun axle stubs and they will clip right into any '99 and up Subaru R160 VLSD and will engage the VLSD and work just fine! The machining cost only 60-100$
This makes the total cost for a 4.11 VLSD under 200$!!
Thats a real ratsun price for an LSD!
some pics of the machinging: http://www.the510realm.com/viewtopic.php?f=3&t=3881