Installing the LSD is like installing any diff or spool in a VW transaxle, no harder or easier. A Thing diff will bolt into a Beetle trans just fine. Make sure that you have the real
thing before going through the trouble since most, if not all of the Thing LSD transaxles were coded AV and AW. The AL comes up with a 3.88 ring and pinion which isn't usually found
with a Thing transaxle
We haven't done an LSD yet, just a spool, so I'm not sure if it will need to be endlessly adjusted or shimmed or have the surfaces blued and run through a rotation or any of that. You'll need to talk with one of the builders out in California for the details, no biggie I suspect. The spool was just silly and stupid and lots of fun, easy in, and the car went insane. Mostly hopped around like a Bunny and kept trying to roll over on it's back. Luckily it came out as easy as it went it.
Any limited slip is going to increase traction greatly, like maybe double it. It's gonna will run hotter and need to be cared for, use a gear oil with an LSD additive. No real minuses at all though, really. Probably take the time to "build" the rest of the transaxle as well, maybe even swap out the CVs/axles for stronger ones.
Make the whole "posi" experience a positive one . . .
The LSD option used to be considered rare, people even turned to Quaife as an alternative, now they're turning up everywhere. One of the plusses of the internet. Still, you might just want to sell it and add the coin to the cost of having a custom box built with all of the bells, whistles AND an LSD.
Otherwise, get on in there and do some damage.
Luck,
TC