[YerDugliness]

I'm considering the purchase of a kit that is reported to have a 1989 T5 transmission. According to this Car Craft article, there were two different T5's produced in 1989, and the latter is much preferred, apparently better quality internals. Here's a chart from the CC article:

RATIOS
1ST 2ND 3RD 4TH 5TH REVERSE
'83-'84 2.95:1 1.94:1 1.34:1 1.00:1 0.72:1 2.76:1
'85-'89 3.35:1 1.93:1 1.29:1 1.00:1 0.68:1 3.15:1
'89-on 3.35:1 1.99:1 1.33:1 1.00:1 0.68:1 3.15:1
Tremec 500 3.27:1 1.98:1 1.34:1 1.00:1 0.68:1 3.01:1
Tremec 600 2.87:1 1.89:1 1.28:1 1.00:1 0.64:1 2.56:1
Tremec 600 2.87:1 1.89:1 1.28:1 1.00:1 0.82:1 2.56:1

So, how do I ID the transmission as being of the " ..'89 on" variety? I don't mind getting dirty crawling around under the thing if that's what it takes.

TIA for whatever info you can provide. Bear in mine that I'm not at all familiar with the internal workings of the transmissions, I'm hoping for some sort of external identifier, such as a tag or some number cast into the case, that will give me a definitive answer to this question.

Again, Thanks!