custom = meaning factory "Custom Cab"
kustom = meaning modified http://en.wikipedia.org/wiki/Kustom http://kustomkempsofamerica.com/

Here are some photo's. I gotta say the 60-63 dashes are so much better looking than the 64-66:
http://i645.photobucket.com/albums/...t%20Truck%20Stuff/image0_zps7b7d30e1.jpg

http://i645.photobucket.com/albums/...Truck%20Stuff/0529120902_zpse17c7b71.jpg