Lots of pics here - Guy's R/C conversion of a model HB.
The base vehicle - a Mini. Note rear rostyles! The whole Viva axle is fitted, along with drive-gear.
Build up each front stub axle using a rostyle drilled out to turn on its original axle, then fit it into the mini upright.
Cut the front axle assembly off the chassis and extend it with two ali strips. Be careful of the fine wires which run to the steering system, which is two electro magnets. When energised it pulls a permenant magnet towards it, which in turn pulls the steering.
Then make up brackets to secure mini chassis onto the viva shell. Rear is easy with just an extension plate. Front is difficult as shown with the clamping sort of plate. This is then screwed to the viva shell and the chassis is held tight in it. Have yet to put a screw and bar across the extension plate holding it to this front plate.
This pic shows why you need to extend this mechanism.
Mini tyres have better grip. Windows need blacking out so you can't see the mech inside.
Viva tyres are more in proportion but stick less well. Hole in body for boy racer aerial serves a purpose.
Last pic