converting rearend
 

90 2500hd 8 lug wheels. I want to know where to buy the kit(s) to convert my rearend to posi track/limted slip rearend?

You prolly have a 14 bolt rearend. You can google 14 bolt posi and find what your looking for. Eaton is a great brand. I had a detroit locked dana 80 in a 81 f-250. That was the best rear axle set-up I've ever had.

I have 3.73 ratio. I dont know if you guys know what brand of rear that is though.

The easiest way to tell, count how many bolts hold the diff cover on, I'm pretty sure its a GM 14bolt. A 77 chevy 3/4 ton has basically the same 14bolt my 2007 3/4ton has, Except I have disc brakes, thats the biggest difference. I doubt you have a GM 10bolt, thats a half ton axle, the light duty 3/4 tons had a 10 bolt 6 lug i beleive.
my 07 has 4.10s But it's still a GM 14-bolt. If it had 3.73s it would still be a GM 14-bolt. Some are known as a Corporate 14-bolt.

ok but I have drum brakes on my rearend though. 16in wheels too.

http://www.rearendparts.com/product.php?productid=645

Theres you a link. You can call them and find what you want for your application, You should have a full floating 14-bolt rearend. Full floating means, at least to my knowledge, you can pull the axle shafts out with out opening the diff cover, theres no c-clips holding the axles into the diff.

thanks for the info.

I decided to do a complete axle swap. I 'll be swapping my 3.73 ratio for a 4.10.1 limited slip axle.

is this going into a 2wd?

yes, going into a 2wd.