It shouldn't be too hard - do you know if any Ford Club Wagons came out around that time that had arm rests? Because then it would just be a matter of finding someone selling some used ones to put on. Otherwise, there are plenty of seat designers out there that make replacements that can fit many vehicle models, and you could just look for a seat design with armrests you like.
Yeah, this is a pretty simple job. The job itself just involves taking a seat out and putting a new one in. There are a lot of places you can get seats. Sometimes junk yards take the seats out of old vehicles and stores them in a warehouse to keep them nice.
It looks like they just bolt to a base. Seems like that should be pretty easy to replace with pretty much anything, as long as it has holes in the bottom of the frame, right? I'll just need to make sure they're the same width so they bolt properly, I think.
Would you need a great deal of special equipment? I'm interested because I'm also thinking of replacing some seats. I don't have a great deal of fancy equipment in my shop, just the minimum tools.