HEI in Mopar ECU casing

GM HEI's not only have a metal bottom on them, but thermal conducting grease is an absolute requirement. Some should come with a new module. For a used one find a tube of "Arctic Silver." Something like copper bearing anti-seize will not work. <- That's experience talking there. Worked for a short while and then made me really late to work. From that experience I would also strongly recommend NOT mounting it to the engine.