Disc brakes 67 C10

[SoS]

Hi
Pardon my ignorance but I'm new to C10s & this forum. We are in Australia & it's hard to find anyone here with accurate info on Chevy trucks, we recently bought a 1967 C10 Custom cab, the chassis no. is different to the cab vin no. so I'm not sure if the chassis is a later version or not.
The problem we have currently is that the truck has what appears to be a factory front disc brake setup & we need to overhaul the calipers. Nobody here can find a listing for caliper kits & they are saying 67s never came with disc options.
Can any one give me some accurate info re disc fitment to 67's & a possible lead for caliper kits

thanks in anticipation
Richard