E body Kelsey Hayes on an A body?
Let's see if i can shed some light on what you are asking of us here on the forum.
First of all there is no such thing as a factory 4 piston disc brake set up for the E body cars.
By that time everything was single piston.
Do you possibly have a 66-69 BENDIX brake system that was used on the B body line of cars? Those are 4 piston calipers.
Pictures of what you have, would be of lots of help here.