The in tank fuel pump will not cause any problems to the CP3 injection pump as fuel feed pressure is controlled by the CP3 pump and any excess is returned to the tank via the return fuel line! While a very low pressure pump may suffice and prevent unwanted air induction into the fuel, the in-tank pump is by design what is used on Dodge Cummins diesels!
My 98 Dodge Cummins feed pump supplies ~14 psig pressure to the injection pump, basically the same pressure as the one I installed in my Jeep CRD. The Carter in-tank pump that I used is the same one designed and used for the later model Dodge Cummins diesels. So the Dodge engineers must have felt that the pressure was safe when they designed that system?
Dodge does not even sell or supply an externally mounted fuel feed pump anymore, and the retrofit replacement pump they sell through Mopar is now the in-tank feed pump that pumps 14 psig just as the one used by some in there Jeep CRD's. It is
NOT a high pressure pump as used in gas models!
I also feel that the in-tank fuel pump is the cleanest installation using existing plumbing and requires no modifications other than the addition of two wires to the pump assembly from under the back seat connector. Anytime you cut fuel lines and add additional fittings, clamps, etc. there is a possibility of leak points in the fuel system.
Also having the additional feed pressure allowed me to add a secondary 2 micron fuel filter that further protects the CP3 pump and injectors...
information on the in-tank fuel pump and installation can be found on this forum in several threads; read all the information available and make a good decision....
http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?f=5&t=78950&hilit
_________________
Supporting Vendor and Moderator of LOST05 Jeep Liberty CRD Limited 
Ironman Springs/Bilstein/Shocks
Yeti StgIV Hot Tune
Week's BatteryTray
No FCV/EGR
Samcos/ProVent
SunCoast/Transgo
Carter Intank-pmp
2mic.Sec.Fuel Filter
Flowmaster/NO CAT
V6Airbox/noVH
GM11 Bld.fan/HDClutch
IronrockArms/wwdieselMount98 Dodge Cummins 24 Valve