I ran across a guy that's building a Triumph bobber using a 2004 Bonneville engine. Here's a pic of the bike in progress.
He posted about it on triumphrat.net, and he has a complete gallery of build pics at
chopperweb.net. That url won't work for you until you register at chopperweb.net. If you don't want to join there,
Bitter End Choppers, who did the frame, has a 4 pic overview of the build progress. At chopperweb.net, MIDGET11 has posted 2 pages of build pics so it's worth joining if you're interested.
I've invited him over here to tell us more about it, and to share his experience as he puts everything together. Hopefully he'll show up sometime soon.