Ok here is the deal. I know for sure that painless is a universal harness for these years. Don't know about the other though. Basically if it is universal you are going to be slicing and splicing till your fingers are raw because you have to use all the original connectors.
1968 F250 LWB 300-6
FORD=First on Race Day
MOPAR=Mostly Old Parts and Rust
I was down for the Ford Carlisle and York Rod show and saw most of the electrical vendors. I don't think you'll be cheated on any of the kits, but; they are universal. So as stated you will be doing alot of wiring. The Ron Francis kit uses a much more robust fuse panel while the others (Painless, EZ Wiring) use a basic GM type knock off. Not that its bad, the Ron Francis you're paying for the little extra you get. The painless also has the wires connected to the fuse block and you fish from there out, the Ron Francis you fish the wire and then make the connection at the fuse block, different view on how to do it. After looking them all over, the Ron Francis is a beautiful kit if you're willing to spend the money, the Painless is good and more affordable and the EZ wiring is good and again a little cheaper cost wise. They all offer nice additions for extras you may want. I'm trying to decide which one to get for my rehab next year. One last thing, if you go to one of the big shows they offer some nice incentives if your ready to buy. Good luck.