Actually LL it was childishly simple to avoid that mix up
First of all we used an Onboard Performance Tool, OPT, resident in our iPads to calculate all performance. We started with the a/c rego which knew the engine type without our telling it.
The biggie was that if you tried to use RR data, finding an EPR gauge would prove difficult.
Just BTW, the GE -400s we bought in were 1 from KAL and 2 from MAS. Both MAS airframes had huge problems from previous poor maintenance practices and cost a fortune to fix while the KAL had a rudder buzz felt through the pedals which took a hell of a long time to fix. It wasn't quite strong enough to give you a foot massage though.