I was going to do exactly what you were going to do mate, but it's just a DAFT idea when you add the costs up..... A decent shell with a clean ID is 4k min, engine 3k for a goodun, gearbox 350, diffs 250 , blah blah blah, just buy one whole mate, so much cheaper in the long run.
If you still want to build a shell, double your budget and add 3k
