The V6's had varying OD's as you can see on Mongo's list. Seems the later S10's (on the whole) had better OD's, '87-'89 and such.
The metal tags to look for are on the left side of the tail shaft housing, attached with housing mounting bolt. They're easily swapped out so beware. There's also usually a sticker on the top cover with numbers that should match the metal tag. These are pretty much the only numbers that matter when trying to identify.
Print out Mongo's list and have it handy when you're at the meet.
I used a V8 World Class T5 for my swap. I opted not to use an S10 tail housing and instead modified my bench seat to accomodate the further back shifter. I like the position a lot. Feels good. My OD is .63 which is great 'cause I've got a 4.57 rear.
You can check out pics and text of my swap from beginning to end on my yayhoo! group:
Kustoms-and-Sleds You've gotta join the group to be able to view the "Files" but, you can un-join if you wish after viewing. I tried to be as thorough as I could with pics and info.
-David
