Here’s a parts diagram for the newer style and other info you might find useful. Up to 1956 the tanks had an aluminum push button and push rod. In ’57 they went to a black button with two riveted disks on the diaphragm. In ’58 the mushroom shaped button with a single disk for the return spring.
There is a kit 377327 that can be used to upgrade ’57 to ’58 style.
