Neat! That's a really cool engine. A lot of guys like to talk about doing stuff to be different; I bet you'll be the only guy for quite a ways with a 503! The giant gasoline truck engines like that are a really neat part of history and very rare to see nowadays.
For the wheels, you might try looking through the Accuride wheel catalog (or similar) and/or calling them and asking about it or something.
http://www.accuridewheelendsolutions...ummer-2011.pdf