How to tell a c-20 from a c-30

[kandeservices]

Hello,

We just bought a 1980 chevy truck with a dump body from a salvage yard. According to the vin number it is a 1980 Chevrolet two wheel drive C-20 cab and chasis built in Baltimore. I am having a hard time getting brake parts for the truck. The parts coming off the truck do not match what is listed. The truck has dual rear wheels and eight lug wheels.

Can anyone tell he how to tell the difference between a c-20 and c-30? Also, can anyone give me a clue how to find rotors, calipers, and flexible brake lines with out using the vehicle description?

Thanks,
Karl
K and E Services