Check with American Autowire. I did a '53 F250 conversion from 6V + Ground to 12V - Ground with an alternator last year; used one of their harness kits for the '53-'56 F-series, and it was a nice kit. I had to make a few changes as I relocated some electrical items, but they were good to deal with. Best price was through Summit.
It's a task that will definitely occupy your mind and take some time, but it was rewarding and trouble-free.
Using one of their generic harnesses in an FJ40/LS custom build right now. The generic harnesses use GM-style plugs, but it's not hard to change that stuff if need be.