FAST Modded Shift Shaft, FAST Easy Spring on Shift Pro Detent/Roller is what's in my 87 and it shifts great!
Did you already put the cases back together?
if so, that sucks.
If not, then send your complete transmission to Cameron at RedLine.
Not sure if he needs your lower case half too, but give him a call and ask him what he needs to perform his Pro Mod to your transmission.