#1. "RE: Norton motorcycles" In response to Reply # 0
Norton first offered the disc brake as an option in 1972, with them becoming standard on the 1973 model year. Rear disc was offered only in 1975.
No Commando is to be avoided, some just may need more work to make them the way you like them. Early '68 Fastback had a frame which should be replaced, but most already have.