Something like
http://gamerabaenre.com/?p=678 thats been in our Hobby domain for ages. I was also thinking that cars should be fairly easy- dip a 1/43 in until you almost submerge it, let the sillicon dry, remove 1/43, cut the mold in two, then fill it with whatever material you want of whatever thickness you want and viola.
I wouldn't even mind trying this with my putty alone, but the only real problem is that 1 body's mold would take up like 5$ worth of putty lol! Let me ask you guys, who'd buy resin/putty bodies for say 15-20 shipped?
Here's an example of MY method:
