Those are weird to say the least. The lower mount is from who knows what, and the upper mount is awkward as well. I kinda doubt these are OEM. The quality just doesn't look to be there.
Re: Exterior mirror set with swing-out extension for towing - NOS
The upper arm is too straight, the mirrors would point towards the sky if they were mounted on a Dentside and the bottom bracket probably wouldn't even touch the door. The mirror heads are correct for 80-82 trucks and vans, but the rest is just wrong for the entire Ford pickup lineup, and even the Econoline.
I'd be willing to guess that these are Ford heads on frames made for a completely different vehicle, but not even a Mazda or a Toyota of that era.
Re: Exterior mirror set with swing-out extension for towing - NOS
The arms on the van trailer tow mirrors must be longer which would put the lower bracket into the recessed body line and that's why the lower mount looks bent.