ATF versus Pentosin Pumps and Racks (Engine Swap Issue)

[VFChris at aol.com]

I'm putting a 3B in a 4000Q.  I'd like to use the PS pump from the 3B  
because it fits well, much better than trying to mount the original 4000Q  pump.
 
The problem is that the 4000Q uses ATF in its system, and the 200 TQ  20V 
donor uses the mineral oil.
 
Would it be OK to flush either the rack or the pump, and switch to one or  
the other fluid?  I'd really like to stay with the ATF.  
 
Alternatively, does anyone know of a pump that VW/Audi used that is the  size 
of the pump found in the 200 TQ 20V, but is designed to use ATF?
 
I hope you all see my issue.  If anyone has any helpful ideas, I would  
appreciate it.
 
Thanks,
Chris
_VFChris at aol.com_ (mailto:VFChris at aol.com)