Heel Toeing is something I struggle with. I decided when I built my pedal setup that I would make the gas pedal completely adjustable so I could hopefully get it right.
The pedal tread is adjustable up down laft and right via the counter sunk cap screws holding it in place.
The pedal is on a threaded boss so you can change the pedal height without changing the travel or throw. You can also set the face of the pedal on an angle. I've also incorporated an adjustable back stop so the pedal bottoms out on the bulkhead rather than stretch the cable.
I've been on the track twice with it now and I'm starting to get the hang of it. The first time out I played round with the adjustment and now it's pretty good.
Cheers