It is possible to mod it from the Mclaren MP4-5B, but you need a lot of modifications though..scratchbuilding etc..
Check out this Japanese modeler:
http://www.asahi-net.or.jp/~xr2h-fkd...p46/mp4600.htm
I guess it might cost a bit of money, so saving up for the 1/12 is also not a bad idea