The simple option is to just use WorldGT parts, after all they use exactly the same rear end as the Super F1. If you are planning on racing it then you will need to modify it to make it fit standard F1 wheels, the problem is almost every F1 kit uses metric 6mm diameter rear axle so they won't drop in without a little work. The exception is the HPI F10 which also uses a 1/4" axle like the Super F1, the problem is the
HPI ball diff set has a
list price of £65.
You can fit a much cheaper Tamiya or Tamiya compatible rear axle in there by opening the holes in the rear height adjusters to 10mm and using a pair of 6x10mm flanged bearings. Standard F1 axles would then drop straight in. You can fit F1 wheels on the front using Tamiya front steering arms.
The wider F103 tyres which you would want to balance out the front width are around 55mm in diameter, so should be just about big enough. The narrower F104 tyres are 60mm in diameter, but they will make the rear end about 20mm narrower.