Obviously original NOS parts are probably the best, but most of us are priced out of the market for those parts. As for the rest I would say panels stamped in the USA are first choice with the made in Asia panels being second. For the most part you are going to be limited in choice as most sellers all get their parts from the same sources. On rare occasions you will see an actual part have options. The biggest difference is the sellers tech support or backing of the products it sells.
You are fortunate though that the 64 tends to be the one year that I think if you had to you could build a complete car body out of new panels.