Good day HerrOtto. Yes the C-10 is the generic ID for a 1/2 ton. Your C-14 is a short wheelbase, the C-15 is a long wheelbase. Fourwheel drives were K-14 / K-15
The 3 cables are still available from various vendors, advise them as to what wheelbase you have.
The rear ones do mount in the round holes in the lower part of the backing plates. You will need to remove the brake shoes to squeeze the "fish gill" retainers on the cable.
Have fun with your new found truck.
Howie