Others may be in a better position to know, but I would swear that not only did 1350 San Bernardino have the KCKC calls in the 50s, but that they had a Spanish language format. An older sister kept her radio glued to 1350, and I can clearly remember a musical ID:
Female singer: "K-C, K-C, San Bernardino"
Male voices: "Sing a little louder!"
Female singer: "K-C, K-C, San Bernardino"
Male voices: "Cha-cha-cha!"
This was back in the day when legal IDs were required every half hour, so it seemed like the above jingle played very often.
Arrinda Homes was a frequent commercial sponsor, and seemed to lead off every commercial break. They had a Mariachi-style jingle in their commercials. This was the Eisenhower 50s, San Bernardino was a growing town, and new homes were being built all over the area. I saw Arrinda signs at several new home sites.
I seem to faintly remember an MOR "Good Music" type of format in the early-mid 60s, but I was a confirmed rock n' roller, and not paying much attention to non-rock radio. I remember the station that came to be known as K/MEN 129 was KITO Country until March of 1962 when the change to K/MEN happened.
KCKC went Country in 1966. If there had been another Inland Empire Country station between 1962 and 1966, I don't remember it.
Just some youthful radio memories.