There is an international convention in place in most racing rules that 1/24 scale slot cars should be no wider than 3.25 inches, or ~83mm, if you prefer. This is done to make sure slot cars can pass each other without interference on commercial tracks which have traditionally been built with 4 inches between lanes. Based on the specs posted on the ScaleAuto website, it looks like all of their existing 1/24 models max out to 84mm in width (technically illegal, but irrelevant for your purpose). I found that a real Huracan GT3 is 2221 mm wide, which converts to 92 mm in 1/24 scale, so it seems that the ScaleAuto body is narrow by 8 mm, or about 5/16". Now a real Audi R8 GT3 is supposed to be 1940 mm wide, or 81 mm in 1/24. It looks like the Nunu chassis might fit under the ScaleAuto body based on width, but I don't have any wheelbase specs. And who can say if the Audi kit donor is exactly to scale as well? I think their are too many variables in play for anyone to tell you without actually having tried it themselves, and even then you would have to accept that the Huracan will be a little narrower than it should be. (The ScaleAuto body length is close, 185 mm versus 189 mm for Huracan and 185 mm for Audi in scale).