If they cut the wires, you can repair them fairly easily. Considering the age of the wiring, you might want to plan on a future rewiring of the entire truck, though. You can do a quick patch job using commercial bullet-type male/female connectors that you can buy from NAPA. These aren't the "official" connectors, but they will let you do a patch job that will let you drive the truck and see what's happening on the gauges. If you do a complete re-wire down the road, it's easy to add the extra wires needed for turn signals at the same time. You can buy a complete harness with all the correct wires and connectors, but you will need a handfull of connectors and pieces to repair the stubs for the taillights, marker lights, etc. You can also use the old harnesses as a pattern to make your own new harness, but it's easier to buy whatever you can and then make the odds and ends yourself.
If you have to install some of the original Douglas terminals on wire, you have several options: you can solder them on (this can result in broken wire since the solder wicks up into the wire and makes the connection stiff), you can use a Buchannan commercial crimper (cost is about $ 65 - it's a little large, but it works), you can track down the old motor pool repair crimping tool (cheaply made - most are worn out by now), or you can track down a military grade crimper (Daniels or similar - these are the first choice, but can cost $ 400 new, and usually about $ 100 used). Terminals and parts are available from Saturn Surplus(?), and I think Erik's also has them. Regardless who has them, they get expensive.
Let me know if you need connector parts - I have the connecvtors, shells, grommets, and all the rest on the shelf - I may have a military (Daniels or equivalent) crimper left as well.