A previous owner changed the mirror set up on my 53 P.U. I have ordered original style replacements but am unsure how to relocate the original holes. Are there steel backing plates with bolt holes behind the sheet metal to attach the mirrors? I would prefer not to have to hunt around from the outside with a grinder. Looks like I will have to completely pull the heater for access on the passenger side. Also would appreciate any tips on filling the holes that will be left on my doors.