Dang, NAPA likes to jack up the price for those jack nuts.
From what I could tell on the 84 Suburban which had the tripod towing mirrors, and the measurements I made, it looks like the two Dumbo mirror holes would be kept and the third upper hole on my door would accommodate the long three screw upper bar on the towing mirrors (5.25" center to center on the Dumbo mirror, then another 5.25" to the third hole overall, for a total three hole span of 10.5".) The lower two holes would line up with the lower bar of the tripod mirror - a total of 5 holes in the door. I think those trailer mirrors might have been a factory or dealer option because they line up correctly with the two Dumbo mirror screw holes.
I really don't tow hardly at all, so I don't "need" the trailer mirrors, but they are in remarkable shape so I hate to see them get crushed with that old Suburban. The even have what look like original blind spot mirrors which seem to match the profile of the larger towing mirrors. Obviously, these are old skool mirrors and stick out past the door even in non towing mode, but they do look "period correct."
I see a lot of great rust free vehicles go to the crusher at the local
Pull A Part. After a few weeks, they just scoop up an entire row of vehicles and dump them in the crusher. I have seen some late model vehicles with no body damage and paint in great condition go to the crusher. In the past two years old squares have disappeared from the junkyards. I suspect that people are paying more than scrap value (maybe $300) and that is keeping them out of the junkyards. Even junk squares are for sale for about $1500 on the local CL. 4WD squares are usually $2500 and up even if they are not running.