I couldn't stop thinking about this so I did a few calculations on my own.

Assumed the rear axle was some kind of bolted to the ground and there was no torque lost due to chassis flex then the rear wheel torque needed to lift the car would have to be bigger then the momentum caused by the weight of the car and the distance from the center of gravity to the rear axle:

Te=m x d

Te is engine torque required, d is distance from rear axle to center of gravity measured in foot and m is the mass of the car in lbs

This would mean a 2000lbs Shelby Cobra with a 90" wheelbase and a 50/50 weight distribution (center of gravity in the middle of the car between the front and rear axle) would need 7620 ft lbs rear axle torque to lift the car... o.k. this still needs to be divided by the 1st gear ratio multiplied with the rear end gear ratio.

With 2.32 first gear and 3.50 rear gears this is 938 ft lbs.


Pretty much, but in fact this much torque is not required. First there are some things I didn't consider (i. e. vertical center of gravity, the weight behind the rear axle causes a momentum in the opposite direction that will help rising the front etc), and second this is more of a dynamic process than of a static.
So mass inertia is also a big factor and the required torque diminishes as the front of the car lifts because the center of gravity is moved rearwards. That's what all the weight transfer stuff during launch is about.

The calculated amount of torque needs to be divided by a factor that depends on the ability of the suspension to transfer the weight of the car to the back, traction, chassis and suspension flex and many other things I forgot.
I think you could figure out some kind of formula by doing some tests with several cars that are able to pull the front wheels, but it will be a bit complicated.

Overall the car has to be light, rigid, center of gravity moved rearwards as far as possible and as much engine torque as possible (although a heavier engine will incerase the amount of torque needed cause it's got to be lifted with the car ).
And of course you need excellent traction.

Maybe some of you who have or had a car that can do a wheelstand can tell us more about the setup of their cars?

And by the way maybe I screwed up with some of the numbers above as I'm more used to the metric system...

And these are only my considerations anyway and could be all wrong as well (So don't absolutely count on it!)