Are you running the stock electronic ignition? If so you may want to try a new box. I had a high speed overheating problem this summer. Kept chasing after dead ends. Well a friend told me he had the same issues before and he ended up changing the box. Solved the problem. Turns out the box was leaning out at high RPM. I changed mine, problem solved. When those Mopar boxes are new things run great but they go away things can haywire.