CA - Mike explained it best. It's the distance between the back of the rear cab wall and the center of the rear axle. Chassis cabs commonly are available in 60" and 84" models, but there are two longer ones available in regular cab configurations (most long bed pickups are around 56").
CC - The crew cab is the one with four full sized doors. The extended cab is 1.5' shorter and called a Supercab by Ford. I think Ford is the last to keep the suicide rear doors which I liked for accessing rear cargo - The rest use narrower rear doors that hinge forward like a crew. The regular cab is almost 3' shorter than the crew.
