Moving this to the top for a bit since so many folks had questions about it.
Update 3: Found the build thread! An alert reader over on ADV rider found the build thread on this bike. A lot of folks have been asking for more info so here you go!
From the comments (Thanks SakeRacer). More info Here: http://www.pipeburn.com/home/2010/9/9/1973-yamaha-rd250-street-tracker.html
Sorry to Pipeburn. I didn't realize it originated on their site. TONS of great stuff over there so check them out often.
My observant commentors make some good points about the classification of this bike. Tracker of Bobber? I see a lot of elements of both styles here and to be honest I'm not crazy about pigeon holing bikes all that much so lets call it a tracker-bobber. Whatever you call it it's still freaking cool!
That's got backroad fun written all over it.