here is a link that supplies some dimensions on oem fans that are popular candidates for swaps. I have been meaning to see if the GM HHR fan would fit a Regal but I never do.
Note that all three of these fans pull some amps as compared to a lot of the aftermarket fans that claim big cfm but give no specs as to how they were tested. Use one of these and you need a good alternator and some decent wiring. Good thing about factgory fans is that they not only were built to do the job and last a long time, but they can often be found cheap on Rock Auto, or such, or found at a wrecking yard. The big Lincohn fan will not only pull a small child thru the radiator but it will pull Brad and a small child thru at the same time
http://www.460ford.com/forum/showthread.php?t=135721&highlight=oem+electric
