Now I have a question?

Say I want to regear. I can do 4.9 m/s with gen2 rear...but

What about the front? I know 4.875 exists but is that a gen1 2.6 gear, gen1 v6 gear, or available in both? And most importantly, how does that factor into the lsd swap.

I not sure about the 83 I know they are not the same I believe it matters on if it was a early on 83. some 83's have the 82 stuff that was not sold here any how I don't think many would be able to find one any how.... I was young and dumb and trashed the one I had........

The 87 was a transitional year. I used an early 87 and had lots of fun. The d/s v6 cv was 25 splines and slid right in. The p/s c/v has 28 splines and wouldn't work. A 4 cyl jack shaft was the solution. Its identical - just a hair smaller in diameter. The 4cyl & v6 used the same c/v on the p/s so both will bolt up to up to the jack shaft.

If you end up going with the 4 cyl jack shaft remember to change the seals on the new shaft and diff as well or you'll leak oil. Another member found this out the hard way and was kind enough to clue me in before I buttoned everything up.

It's also a great reason to install manual hubs otherwise slippery road conditions can bring some excitement when 4wd is engaged.

Not sure about the gearing. I know that my front lsd is 4.625 and the SR rear is 4.636.

Fwiw - there are two starion lsds already on the parts board here. Tonygon's is complete with a v6 housing. And yeah, the other one is mine...