It shouldn't be too difficult. I believe the axle diameters are the same. If not, the od of the wheel bearings should be the same so yu could put 450 bearings into the GB hub. I usually just get a used dirt bike rim and lace it up to the stock hub using the stock spokes on my CB350 race bikes, but I think the 450 uses a 40 spoke hub and most dirt bikes use a 36. You could use the whole dirt bike racer wheel and a cble operated rear brake. I think some of the late 70's CRs even used a magnesium backing plate. I have been meaning to weigh the bare wheels and get a weight comparison
Anyway, welcome to the board, good luck and keep us informed.
HI Ken, not a racer myself, just like building stuff! As far as i can tell theres a realy good amount of intrest here with brit bikes always has been, the street raceing is very popular always good fields entered for the classic and post classes here in our towns annual race so the jap stuff is getting a good run now.The newest evevnt run here was the Burt Monroe classic, held way down south in Invercargill with beach racing just like the old days. It was started after the success of the movie "THE Worlds fastest Indian" the story is about old Burt Who built race bikes down there. great movie, check it out if you havent already.Steve.