The series designations for the 1/2 ton (C10 or K10) and 3/4 ton (C20 or K20) are used in the '62-'66 Chevy trucks, Apache for the earlier '60 & '61 Chevy trucks. What year is the C/K 1500 truck you are considering for a donor? Although it is possible to transplant a later model cab onto your '66 Chevy C10 chassis, it is more costly and time-consuming, due to the modifications needed at the frame-to-cab perches, etc. Also, the overall value of the truck is diminished on the backend, if you decide to sell.
The C10, K10, C20, K20 & C30 cabs of the same years ('60-'60, '61-'61, '62-'62, '63-'63, '64-'64, '65-'65 & '66-'66) are directly interchangeable. The 3/4 ton & 1 ton rear frame-to-cab perches are the vulcanized rubber style, which are different than the cantilevered style found on the 1/2 ton models.
