tranny brake ....need help

I dont have mouch experience in brake cars..Only one that I've helped wrench on. But, in terms of electrical, you NEED 12 volts present all the time. That's with the fuel pump, fan(s), waterpump, lights, ignition, and race electronics on and drawing amperage. For some timers, this is very critical, same with some ignition boxes. Also, wire size and routing can make a probelm. So, a low cell may have caused the bog from weak spark, and not using the trans solenoid and footbraking helped. Or the carb could be partially openning on the two step, making the engine bog when the brake lets off, and the engine goes lean for a sec. A double pumper is probably the better choice for a carb on that setup. The owner of this car goes full throttle on the 2 step and his two step is chipped 700rpm below flash stall. So the driveline has a little momentum to get it moving. (351Cleveland/ C4....) I think it may take some experimentation to determine exactly what the combo likes, once the electrical system is up to snuff.