HQ-HZ-WB stubs can be used on HD-HR front ends no problems. you still use the original HD-R steering arms so the steering is the same, but not all calipers will fit. I think you have to use either HZ or WB girlock calipers. A lot of hot rods built in 70s & 80s used HR X members with HQ stubs and are still running around. Hope this helps

cheers
Max