Here's a collection to ID them fairly quickly...
(left to right... excuse the 2008 cell phone pic)
1) MP112 - Magnusson aftermarket version of 2003-04 SVT Cobra s/c
2) Gen 5 (Gen V) M90 - 2004-2007 Grand Prix Series III 3800 s/c... 4-bolt 75mm throttle body
3) Gen 3 M90 - 1996-2005 Buick/Olds/Pontiac/Chevy Series II 3800 s/c... 3-bolt 69mm TB, mount hole on top for engine cover
4) M62 - early 1990's 3800 s/c
5) M45/62 (?) - 1990's Toyota or Nissan, I think... it was given to me, and I gave it to someone for a motorcycle project
(pic was over 10yrs ago, I only kept the 1st two for my own projects, so nothing to sell)
There were multiple M90 types... Thunderbird SuperCoupe's (and some Merc Cougar's) came with an M90, but no rotor coating and air-to-air intercooled (eek, not how to do it right... some Aussie's do this, too).
The 96-97 3800 Series II L67's came with a Gen 3 M90 that has a black steep vacuum tree right behind the boost bypass valve, which was replaced with the port in the lower intake, if I recall. Otherwise, it's functionally the same as the 98-05 Gen 3 M90's, if in good condition (you can drill/tap/block-off with an NPT plug, if you want to custom route things).
The main inspection issues are how smooth it turns, how worn the coating is (typical to not be perfect), and condition of the 6-hole coupler connecting the pulley shaft to rotor pack (~$20 part to replace, and re-seal with $7 anaerobic gasket maker, refill with $15 supercharger oil).