The thing about a 727 is that it doesn't shift down to 2nd when slowing to a stop, it drops directly from 3rd to 1st so it'll stay in 3rd at a pretty low road speed. If the road speed is low enough in 3rd when the throttle is floored it'll kick down all the way to 1st and I assume the RH will do the same thing...never tried it with an RE but I think it'll do the same thing.

Just spitballing but I believe an RE standalone controller would need a TPS, a TP cable and a speed sensor...the logic to make them all work together is way over my head.