I have a 350 in my 91 RS that is merely a cruiser and I have no plans to track it or use anything other than street tires. Currently I have a NWC swapped in there that is tired but surviving. It whines louder than my exhaust 1-3 and the 1-2 shift feels like I'm trying to stir up a pot of rocks. I can afford to either rebuild it myself, or buy a used WC T5 and throw it in as is.

Big enough difference in WC to NWC or should I just rebuild what I have so it's fresh?

 

I wouldn't really consider consider changing to the Rev 2 transmission to be an "upgrade". An "update", yes; "upgrade", not really.

Having rebuilt the Rev 1 trans that came in my 83, and many just like it, about a dozen or more times, I would recommend against "rebuilding" it. What goes bad about those is the case stretches across the front and allows the gears to misalign. That's what makes the noise. Positive proof is if it leaks fluid between the BH and the front of the trans; if that's happening, the trans is garbage.

All in all, I'd recommend getting the newer version, but not because it's an "upgrade" in any particular way. Just make sure you get a V8 one. It'll have 26 splines on the clutch gear, where a 6-cyl one will have only 10 or 14 splines, I forget which.

 

A T56 would be an 'upgrade' for any T5.

 

"I can afford to either rebuild it myself, or buy a used WC T5 and throw it in as is."

 

Hey man, you said "upgrade"