2008 Mac Pro - 3 Apple Displays On Radeon 5770

I have an early 2008 Mac Pro that I, long ago, upgraded to an ATI Radeon 5770 HD and have run two 23” Apple Cinema Displays on ever since. I just received a 27” LED Apple Cinema Display and want to run all three on this card. Is that possible?

Traditionally, I have run the two 23” with one direct to DVI and one to a Mini DisplayPort with an adaptor from the display’s native DVI connector. When I connect the 27” ACD to the open/available MDP on the 5770, it will only allow two displays to operate.

23” ACD -> DVI (direct)

23” ACD -> MDP via DVI adaptor

27” LED ACD -> MDP (direct)

Thanks for any and all help with my old school setup.