What is difference between Custom and CST?

[8door]

mac808 . You might be right about the years 67-68 and more CST
equipped later trucks.
I have seen a couple of CST badged 68s but did not list the
trim levels.
My truck, a 68 does not have a SPID, but has:
Rubber floor mats.
Cloth bench seat.
Chrome trim around windshield and rear glass.
Aluminum center buttons on control knobs.
Plain horn button.
Arm rests and padded door panels.
And of course the "Custom" door emblems.