Rocky Mountain does specialize in the older processes, which is probably what they are listing on their website, but they used to do the modern K process once or twice a year as well, they may have changed since I was working in the local photo store, I have not sent any K process film in for a long time now.

The mailers we are getting here in Montana, are addressed to New Jersey as the processing address.

These are the address for the only two labs I know of to do Kodachrome processing:

Kodak Premium Processing
16-31 Route 208
P.O. Box 7000 Fair Lawn NJ 07410-7000
Tel: 1-800-345-6973

Dwayne's Photo if shipping other than USPS then use:
ATTN: Customer Service Dwayne's Photo
P.O. Box 692 415 S. 32nd ST.
Parsons, KS 67357 Parsons KS 67357
Tel: 1-800-522-3940