Igniter boards can be switched and probably thermostats and switches, as long as they operate at the same temperatures and will fit into the space. On an orifice, the key is that it must fit the threads and it needs the exact same size of opening. If it does and is still made of the same material there should be no reason it won't work.
KIRK, DO YOU HAVE ANY SUGGESTIONS AS TO WHAT BRANDS TO LOOK FOR TO FIX THE FURNACE? MY DAUGHTER AND I BOUGHT THIS 1983 TIOGA MOTORHOME FOR THE GRAND DAUGHTERS AND US. THE ONLY THING THAT DOES NOT WORK IS THE FURNACE. SOMETIME IT GET CCCOLD! IN MICHIGAN.