What is the trans oil capacity for a 1977 Chevy C10 with a TH350 trans?

My 1976 GM truck manual says 20 pints, but that includs the torque converter. It says to put in 8 pints, check the stick and start the engine at idle, continue adding oil until the add line, then wait until running temperature, then shift through the gears and fill to the full line.