I recently set up and sold 2 extra diffs using the TG gears.
The V6 set was a Yukon part number TV6-529 and it set up very nicely. The 4cyl set also set up nicely and had a nicer finish than the 1st set with a part number of T8-529. I remember researching the part number and finding a matching Gear/number on Zuks web site where he mentioned they where "a decent gear commonly found in a yukon box". Neither set had any GG part numbers on them but then again neither had a "Made in the USA" mark either.

here are some pics of the V6 set
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90 Xcab V6
3.0 Rebuilt/Balanced
P/P w/OS valves
Downey Hdrs,Jacobs Ign
5.29's,Tru Trac+Lockright
4"TG SAS+Rear Kit on 35's
(DOA Racing = $1200 lesson <img src="/forums/images/graemlins/angry.gif" alt="" />)
www.performancecylinderheads.com