Hi Monty

According to Nvidia:

The model identifier should be Mac Pro 3,1 or 4,1 , or later
(NOTE : Mac Pro 1,1 or 2,1 is not compatible)

There is a driver update available:
http://www.nvidia.com/object/geforce...03-driver.html

The Nvidia 8800GT was the preferred card for the 2008 MacPro
GTX285 was an option for 2009/2010 MacPro
Will check it in a 2008 MacPro here and confirm.

Simon