What's to stop me buying an old car to rob it of it's LPG conversion to transfer into mine?

http://cgi.ebay.co.uk/BMW-520i-Saloo...QQcmdZViewItem

That car is only a few miles from me, and is blatantly not going to end up going for much money... Is there anything to stop me lifting all the gas conversion and it's associated bits out of that, and getting them put into my car (or my next car) as long as it's a 5 series with the M50 engine???

Or am I barking up the wrong tree?