If you use the ls countershaft, ring gear, and diff it will work I've done it, you will need to remove the bearing races from your case if your diff has tapered bearings if its sealed bearings you will have to check the shimming in the case for the bearing pre load, I used a b16 LSD (aftermarket) and b16 countershaft and ring gear in my gsr trans, its the same theory it can be done and will work. And the ls final drive will still rip good with the type r gear set
But as far as mixing and matching countershaft and ring gears , its not recommended but if you have to make sure the "tick" marks on the gear teeth are the same and then you need to use a buffer wheel and go over the gear surfaces, personally its more work than its worth you really should just get a matched set and you can't use a countershaft from a big ring gear with a small ring gear or vise versa , but.I hope this helps,
