Question re: aftermarket LSD and final drive
 

Do aftermarket lsd such as Cusco or the direct drop in os giken super lock affect the final drive?

Final drive is determined by the ring and pinion gears, not the differential. The ring gear bolts to the differential.

Thanks! Thats what I needed to know!

BTW, since it seems that you are unfamiliar with the internals of the 3rd member...

Setting up the ring and pinion requires a dial indicator and grease paint. If you do not get the gear depth/engagement right you will have a very noisy unit and possibly excessive wear.

Most shops charge several hundred dollars to set up a 3rd member, and that is if you bring it to them already removed from the car. If you don't bring it in removed and drive in with a new LSD and ask them to install it, be prepared to pay $500-$1000. Rates vary greatly.