If your RSLinx Pro is talking to your PLC5 thru your already installed PKTX Card then as Ken said all you need is the ABR Driver ( It can be downloaded from Intellution site (Now GE ) http://globalcare.gefanuc.com/
We use Linx extensively as a DDE server with our Fix systems. The Fix DDE driver works very well even with several thousand tags provided that you allow the system enough time to start up all of the connections. The only oddball issue with Linx is that you will need to disable the Thousands seperator in Windows if you want to write values greater than 999 to an AB PLC via Linx.