After looking at an airfix Mini body and the chassis i would say yes it could be made to fit.....if you could overcome some issues.
To my eye the main issues would be the rear "kick up flat" of the chassis would have to be taken off. The slot in the guide tongue would need filing back so the guide could retreat just a tad and the lock screw underneath would have to be very flat or removed if you used 13" rims and tires.ie the chassis parts would need to be soldered or glued together. Chassis width is no problem as there is another narrower line that the chassis could be folded to.


