It sounds like you found some pretty cool lights. I've never done it, but you likely will need a 12v light socket, wire, and possibly a switch. There are many types of 12v bulbs for different applications, and sockets to match, so without seeing your light, it's hard to predict what you'll need. Rebuilding them shouldn't be too hard or expensive. The key is just make sure you keep the wires separated and prevent them from grounding out to the light housing. If the wires go through any part of the metal base, make sure to wrap it really well in tape where it goes through, or better yet, put a metal or plastic grommet in the hole around the wire.
You can probably buy all the parts you'll need either from an auto parts store or online.
The most challenging part will be figuring out how to attach the socket to the light fixture, if it wasn't bolted or screwed originally.
2007 T-286SR Cherry/Granola, #6236, original owner, current mileage: 9467.8 (as of 5/26/19)
1997 T-2653 Blue Denim, #5471
1979 12 1/2' MC, Beige & Avocado, #4639
Past Sunlines: '97 T-2653 #5089, '94 T-2251, '86 T-1550, '94 T-2363, '98 T-270SR