bad coil or ECU ?

OK .. 72 Duster 318 all stock (auto) 2 barrel Carter Just rebuilt, resurfaced, rebushed by a VERY reputable guy.. runs great. the problem I'm having is the car starts up and runs good and idles ok and idles ok in gear as well. but after driving it around for 10 mins it wants to die at a stop light. and it starts right up and runs ok until I put it into drive OR reverse. basically it runs and drives decent until it gets good and hot. Then it runs fine until I put it in gear then it dies quickly. If I let it sit for 15 mins, it then idles OK in gear until it gets hot again then it wont run in gear (on the brake) at ALL !! I have put new plugs, wires, dizzy cap/button, ECU is new also, the voltage regulator is all new and the carb is rebuilt , and it is getting fuel. the only thing I have NOT replaced is the Coil... does this sound like a coil on its way out? runs ok when cold and fails when it gets hot??