88 f250, 5.8, c-6.
Swapped efi engine to early 80's 351w (carbed).

Duraspark II, blue connector icm.
Kept tfi coil with 88 harness, icm red wire to coil+(white wire on coil) with ballast resistor inline,
icm white wire to switched 12v, icm black(ground) spliced to ground dist./icm mount lug to ground lug on intake bolt. Other wires per duraspark diagram.
Icm mounted to metal airbox bracket(cleaned to bare metal).

Icm getting Very hot. Killed one icm before noticing the heat. Replaced icm and runs fine but still getting hot. Stopped running engine until I solve this so I don't kill another icm.

What causes the heat, and how do I fix this?

Thanks,
Sean