5.7 open up not good

The issue with the MDS (multiple displacement system) can be easily changed it's just a lifter swap to nonMDS lifters, but that only works on the 06-08 motors. The 09-up stuff has variable cam timing (VCT) the 03 PCM will not be able to control it, and it could cause issues. Your better off with the 05 for your ram. Or any motor that's 03-08 leave the 09-up stuff alone, unless you have an 09-up already.