Omg as a former California resident (about 20 yr ago), I do not miss the bureaucracy and rules. In MT, older vehicles, like my van, have permanent registration!
I know some RV'ers open a LLC in MT and register their RVs in the LLC. I have friends that have done this and I could certainly ask them how they managed it.
Also, saw you signature line and the bikes...I just acquired a used 2022 DR 650 and love riding it