I am not sure what the logic for labeling them “for 2009 Mac Pros” is, but after searching the entire depths of the internet, I finally found someone who had tried it, and not only found out that it works in an early 2008 Mac Pro, but it works perfectly beside the ATI Radeon HD 2600 XTs that came in those machines.
I have been wanting to expand the monitor selection on my Quad Mac Pro workstation but was having trouble finding a 2nd 2600 at a decent price. After seeing that the GT 120 was available on Apple.com (and in stock at the local store) for $150, vs. $299 for the older card most places I looked, I decided to look deeper.
The comments section on the store.apple.com page lists a few people that had tried it with success so figuring I could return it if I had problems, I picked one up.
I came home, shut down the machine, plugged in the card, booted it up and was in business. It’s worked flawlessly so far as a secondary card, and I am told it works fine as a main or only card as well.
Enjoy!