I worked at a harley dealer back in 1993, we used to have to do that with the steering head as well. Cut it off and send it back. Then they would send a new replacement frame with an identical vin stamped in it to the old one. This was on collision repair deals. We also did stuff with custom bikes using paughco frames and CCI engines. Both the frames and engines came with numbers and certificates of origin. The state would issue a title which had the frame numbers, and as a custom build