There is a lobe on the camshaft that operates the lever arm on the fuel pump. As far as I can tell, 216 and 235 pumps are interchangeable so far as mounting on the engine and being operated by the camshaft are concerned. There are several variations externally, such as the position of the inlet and outlet ports, crimped or machine screws to assemble the parts, and whether the pump moves only fuel or has a separate chamber to boost the intake manifold vacuum to help the windshield wipers work. Two one way check valves keep the fuel moving in the right direction.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!