Differential
 

So!! I bought my 87 N/A with a welded rear end. I was curious if it is possible to just switch the pumpkin with a different stock pumpkin or do I have to change the whole rear end? I want to get an open differential for winter time. Any help is great about this!

You can buy another NA pumpkin and it will bolt right in. There are a few different options you can get. Don't get a TII rear end, it won't bolt to the driveshaft or cv axles, unless you get an adapter driveshaft and TII cv axles. Some NA models came with a limited slip differential, and it will bolt in just fine. Automatics and '88 convertibles came with a 3.90 ratio rear end, vs. the coupe's 4.10. 3.90's are better for mileage, but 4.10's are better for acceleration.

Oh awesome, thank you much!

Or get the miata Torsen LSD, bolts right in

Oh yeah, those are real nice too :) I still use the NA open differential in my TII converted convertible. I've been thinking real hard about getting the Torsen, but I want to wait a little to see how well the NA differential will hold up. Seems to be doing fine though. I don't launch it real hard or anything, so we'll see how it does. I hear it can handle the power so long as you don't do anything stupid.

In my T2 i have the FD Torsen diff, i love it!