I think you should also drill several holes in the bracket to allow air flow thru the empty ECU box. Keep the holes from showing once assembled and none drilled under the HEI pad. Your doing a great job. Keep the pictures coming.
Keep in mind that those ECU's normally run in a 200+ degree distributor normally, so it won't need ventilation.
It will run WAY cooler than it is made to run just mounted to the flat plate with heatsink compound.
