I personally converted my 03WR250F with minimal effort ..... I also have a buddy that did his(son's) 05WR450F and his KLX400, both very easily. He flat smokes on the KLX btw ..... and he's doing enduros on it ......
see my mods here:
http://www.sandslave.com/2003wr250f/
I'd convert every next bike of mine with a plate ...... until they change up the laws so bad it can't be done any longer (like in some states) ........