What is the proper fast idle speed for a 350 C10?

The proper fast idle speed for a 350 C10, typically found in Chevrolet trucks from the late 1960s to the early 1980s, is generally around 1,000 to 1,200 RPM when the engine is cold and the choke is engaged. This allows the engine to warm up efficiently while providing sufficient fuel. However, it's always a good idea to refer to the specific vehicle's service manual for exact specifications, as variations may exist based on the model year and any modifications.