If my t2 engine is bad which one would be the best choice s4 or s5?And would it be a somewhat easy swap to a 91 base model conv..

 

you can sort of plug and play a TII into an N/A ..IF it is the same series.
You can even use the N/A harness with a little "finessing".
It;s been done before,so your info is waiting if you search it out...sorry,it is frequently asked.

 

How do i check the series?

 

s4 is 86-88
s5 is 89-91..