A lot of the melted and missing plugs are available at Napa and really should be installed. Most good auto parts stores (Napa or commercial grade stores) should have the loose female blade terminals with the lock tangs that go in the stock plugs so you can install the correct color and gauge wire ( they'll have these in compartment boxes in the back usually, so you'll hafta ask!). It's best for wires to run their full length without splices and soldering and shrink tubing are the best way to splice wires or attach ends (after crimping)
I was going to try to send you the 65 wiring schematic I have, but it's actually a booklet that requires you to match up the different systems on different pages. Getting one of these booklets for your truck is the best $5 you'll spend to correct hacked wiring. It even tells wire colors and gauges. Get it from LMC truck