Looks like the 1970 C60 Air Brake units were only available with the 427 engine. They had a 6.71/9.14 ratio, 23,000 pound rear with 15x7 rear brakes and either a 9,000 or 11,000 pound front axle.
Mike B
What I should have said was IF you ordered the 23,000 pound 2-speed rear it automatically came with the 427 engine and Air Brakes with the ratios listed above.
The 366 with a single speed 17,000 pound rear was the standard issue at 24,000 pound GVW. The 366 could have the optional 17,000 or 18,500 pound 2-speed rears with either Vacuum Over Hydraulic or Full Air brakes.
The 17,000 pound axles are Chevrolet/GM and the 18,500 pound are Eaton.
Sorry for the confusion,
Mike B
