HEI in Mopar ECU casing

I would suggest looking into using longer transistor screws to hold the aluminum piece in place if you're going to "invert" the module's mounting. I would also use more of the thermal compound between the aluminum and the case after Dremeling out the plastic so that the aluminum can contact the metal case. It isn't enough to simply bolt the module to the aluminum, the aluminum needs to be able to radiate the heat away and captured inside the case without metal to metal contact it will not be able to do that.