if it's rc i would start the chassis because i'll have to put my electric components. make axle guides for the wheel axles ( this could be just a circular slot near every tire so total 4 )
then draw or re-design the cover as one part ( doors-window-trunk-boot) to hide you're electric components .
once that done you can design attachment points to assemble the chassis with the cover ( could be simple couple screw slots).
for the rest of component as wings and rims i guess it will be straight forward
lastly i would highly recommend to buy a cheap rc car and try to disassemble it could give you more insight.
if you need more info i'll be more happy to help ;)