I scabbed a late model harness and fuse block from a junk yard charger for a project. You have to draw up your own diagram though, unless you want to re terminate all the wires with the correct color wire. Great if you add a bunch of junk to your car, not great if you're close to stock. If your car is electrically simple (as I'd imagine a stock '63 would be? ), this not too bad.
If the harness is ok physically and capable of all functions as designed, just untangle it, undo all the crap "fixes" one at a time the right way, and line it up all pretty. This is the best bet if near stock, and no reproduction harness is available. If you take the seats out, this can actually be quite enjoyable and rewarding. I've reached a point where I typically enjoy harness work. Isn't that messed up?