Does LMC advertise their version as OEM? I can state their mirrors will start rusting on the underside within the first year. They also didnt move (supposed to collapse towards the door panel, but instead would just try to take the door panel with it!).
I got tired of playing that game and so found some mint NOS for $250 (pair). My truck is in the shop, but as i recall, the difference between NOS and LMC (in my case) was the nut used to mount the extender to the main bracket. I think the original ford nut was rounded (could be vise versa) so check out some original mirrors and see if that holds true for you. My NOS also close/collapse like the good lord intended! lol.
Christopher in Portland Or. 1981 F250 Ranger XLT 4x4 trailer special 351M, and auto C6