RPM (Richard Petty Motorsports, or whatever that team was called then) was a Dodge team, but someone decided they weren't strong enough to become Dodge's primary team. Petty switched to Ford after Dodge got out, then switched to Chevy, and after Jimmie Johnson bought into the team, switched to Toyota (wait, I thought JJ was a Chevy loyalist!)..
Interestingly, Brad Keselowski is a THIRD-generation Chrysler/Dodge racer before he jumped ship to Roush. His dad, Bob, raced CHRYSLER LEBARONS in the ARCA series in the '90s, and his grandfather John raced Chryslers on Michigan short tracks in the '60s...