i dont care about that but will a th350 fit?

 

Well, a 98 S-Blazer has a 4L60E auto-overdrive trans. A TH350 will bolt up, but you will be in limp mode as the computer won't see the tranny, you will give up overdrive, you have no kickdown cable to communicate throttle position to the valve body, if it is 4x4, you can't bolt up the stock t-case, and you give up converter lockup. A boneyard 60E is $400, give or take. Don't go through the hassle of the TH conversion. You lose more than you gain.