Holy cow! 900CFM....that sucks!...or doesn't depending on how you look at it, lol. Poor flow, coupled with a shroud that basically blocks all other air flow will surely heat that thing up.
I would suggest a Chevy HHR fan. You can get them new for about 50 bucks (I got mine through Rockauto.com) and they pull somewhere in the neighborhood of 3000+ CFM. This is the fan I have on my car, and it works great...and it fits a 22" radiator perfectly.
After burping your cooling system, that would be my next move.