Yeah, the DIVAD had four contenders, one was basically a Gepard on an M48 chassis, one was the Sargent York, one was a rechambered (instead of the original 37mm, it uses the NATO defacto standard 35mm, should be noted that the 37mm version had so much recoil that
it literally shook the vehicle frame apart) Vigilante that Sparky and friends put onto the table, then General Electric's 'slap a GAU-8 Avenger on it, give it some radar, and call it a day' project.
(GE's mockup of their DIVAD contender)
(Sparky and friends contender, the gun is literally the failed Vigilante's Gatling autocannon rechambered for 35mm)
(the oddball which is basically a Gepard style turret with the guns centrally mounted instead of mounted on the sides, uses the same 35mm guns the vast majority of NATO uses for their SPAAGs)
You've got to remember that when the York was being prototyped, Bofors had recently introduced a new 40mm shell that managed to squeeze a sensor fuse -i.e. the
fun fuse that does whatever 'not explode on contact' bullshit is needed, like taking out aircraft or showering infantry with flechettes, mostly known by us today as the 'fuck aircraft' fuse- into. This is a
major game-changer when it came to air defense. Previously,
everyone had to rely on the immense volume of fire to produce results when it came to their army assets. Sensor fuses back in the day couldn't be really miniaturized into something less than three inches (although, to my recollection, the 75mm 'Skyweeper' is the only non-naval AA piece that has a sensor fuse although the pace of aircraft made it obsolete anyway), so the navies were decently protected given radar guidance.
Having it in 40mm while still being effective? If you're a helicopter or low-flying aircraft pilot, then you'll need a new change of pants because you'll be shitting
bricks.