Let me repeat that under Michigan law any percussion handgun that has been converted to fire fixed ammunition MUST be registered via either a purchase permit or RI-60 ( CPL holders ) regardless of whether you carry it openly, hunt with it, lock it in your safe, or bury it in your back yard.
Secondly, there is no law in Michigan that specifically permits the general public to open carry any firearm, let alone a requirement that such firearm be registered. It is the absence of any laws prohibiting such carry that make it legal.
The controlling law is MCL 28.422
The law exempting your '58 Remington is MCL 28.432
Since the only law requiring registration is found in 28.422 and 28.432 exempts percussion guns from all of the requirements of 28.422, there is no law requiring such a gun to be registered in order to openly carry it.