Welding anything to a bare frame is a mistake. You will almost certainly end up with the wheel centers and the fender openings mismatched. If you want a roller, just set the frame on the rear end housing and C-clamp or bungee cord it into place. Then you can hope you put the IFS spindle center in the correct location.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!