I will try to take pictures of how I do my mod.

I plan on cutting the ECM's tin case under the OEM looking aluminum heat sink and then using some 1/16 inch solid copper sheet to cut out a mount for the GM HEI module that is slightly larger than the cut out in the tin case. I will use two tapered head 8x32 screws to mount that copper sheet to the back of the OEM heat sink with heat sink jelly and fake Trans cap. Then two of the same screws to mount the HEI module with that jelly to the underside of the module to copper sheet.

This should wick away all the heat into the OEM looking aluminum heat sink.