Bob, welcome back to the fleet of Tall Ships. I only got to work you once on the CCA AM100D, but I look forward to hearing your latest soon.
You won't need much cooling on those 4-400s in ICAS, maybe just a muffin fan parked to blow on that shelf from one end to the other.
But if you wanted to have it look stock, the blower motors are fairly generic, and can usually be fitted to the existing shroud, mounting flanges, and any ductwork if that 1R is pressurized, I forget.
I got a new (old stock) one from Fair Radio that went right into the 300-G, but there are industrial houses that supply current production, but they cost a piece of change too.
Try the Grainger website for the motor itself -- and pick around for an assembly if you need more than just the motor.
I did a search for motors at this link.
http://www.grainger.com/Grainger/wwg/productIndex.shtml?originalValue=blowers&L2=Motors&operator=prodIndexRefinementSearch&L1=Blower
