63-66 horn set- where to buy?

If you simply want a horn that works, almost anything will work. In my 1964 Valiant, I use the little horns which were on the pusher-fan support rod which I installed from a 1980's M-B 300D. I think the OE horn was just a single in 1964 since that was all that was in it, though it did have other non-Mopar parts (radiator, Honda battery). My 1965 Dart has two horns (hi and lo) which take up a lot of space. Given that, owners adding stuff to their engine bay may have left out the factory horns, so might be available. I vaguely recall that the horns on my Chrysler minivan have simple screw-lug connectors.