I would certainly put a fuel cell in, to allow the installation of a dry-break fuel filler. It's not legal to do so with a stock tank and a quick-fill and dump cans is both faster and safer.
I did make sure to leave all of the heater, defogger, rear wiper, horn, and other electrics functional on my car, specifically with enduros in mind.
Make sure that the floorpan and firewall are sealed to keep out water. Water = steam = fogged windows.
Start with all new wear items - wheel bearings, hubs, etc. rather than waiting for them to break before replacing them.
K
EDIT - Install a REAL muffler.
[This message has been edited by Knestis (edited July 29, 2004).]