That's it. As no 1955 "first series" 3100 (i.e. Advance Design models from the first part of the year) seems to exist in IMCDb, there will not be a mess with that MY. All 1955 Chevrolet pickup trucks here are (or seem to be) TF ones.

And Apache/Viking/Spartan can also be put as extra info for (only) 1960-1961 C/K-Series models too.
(The fact is there is only 38 "Apache" for '60-'61 Chevrolet trucks in IMCDb, no Viking nor Spartan)

Thanks!