I've bought a lot of stuff from Classic Industries over the years. Some good, and some "not-so-good". They too have a lot of the Chinese produced reproductions that are junk however, they also seem to have a good lot of GM/Delco OEM parts.

This may work for your truck as it's a GM part:

Truck Parts | 1962-1966 | 1962-64 NOVA & 1962-66 GM TRUCK IGNITION SWITCH | Classic Industries

You may also need the "innards":

Truck Parts | 1947-1966 | IGNITION LOCK WITH OCTAGON KEY | Classic Industries

As a second option - I have had really good luck over the years at local NAPA parts houses as they tend to have a lot of OEM stuff and they'll take it out of the box and let you check it out before buying it.

Good Luck,
Glenn