FYI:
mobileparts has his brake systems confused.
BENDIX brakes were used on the 66-69 B BODY line of cars, and are 4 piston calipers.
The brakes that are used on the 65-72 A BODY line of cars, with the 4 piston calipers, are KELSEY HAYES brakes.
The Single piston, sliding caliper, brakes that you are inquiring about are also a KELSEY HAYES manufacturer, used on the 73-76 a body cars.
Don't have a "part number" to give you as i never have seen a part number on a caliper, other than manafacturer "casting" numbers that i don't know much how to decode.
There are various Kelsey Hayes calipers, depending body style, year, where, and how, the brake hose attaches to the caliper.