Hi,
Only the basic trim C10, C20 & C30 , K10 & K20 models were available in SA, (Custom & Custom Deluxe trim). No Crewcabs as well. Also the interior & rear differs from the US versions as well, furthermore they only sold about 6k units in SA between 1973 & 1980, this Trucks were discontinued when the 1981 "Silverado" version appeared with the square headlights.
I will attach a pic of my C10 to indicate the differences later on.
Paul C10
South Africa