If I remember correctly there are both ISO and ANSI standards for things like the height off the floor for hanging pedal assemblies. What I think I would do would be to measure the from the center if the VW pedal pads to the floor then, if you have a car with hanging pedals make the same measurement. I even might go to a dealer or used car dealer and ask if you could get some measurements to see it there is what seems to be a standard height off the floor then use that. Check trucks, sedans and sport car style rigs.
A lot of the floor mount pedal assemblies for rails can be mounted upside down and you rotate the MC's 90 degrees to give you a hanging assembly. I agree with the dual brake MC cylinders w/a bar between them. The bad thing about the hanging pedals with the cylinders facing the rear of the car is the distance between the dash and the firewall. The one picture I showed of the buggy with the hanging pedals had a tube mount made against the firewall to strengthen things up. I can post pictures of that if you want (maybe I will post the pictures, in a while, just to complete what I am talking about). Access to the cylinders behind the dash might be a bit tight unless there is some fancy and creative thinking done.
For heel and toe (its been a long time since I have been around auto X-ing but the video I have seen kind of looks it is 1, 2 and rev the pudding out of it. You still could need the heel and toe rather than the cross-foot braking method) the gas pedal is mounted slightly behind the brake/clutch pedal assy. You should be able to get that information at the same time you measure for the pedal distance off the floor. Also note that the gas pedal is usually tilted towards the center of the car as that is the way feet usually like to work.