iirc, some buick and/or pontiac 455's had 'em too. but find any 68-76 caddy with a 472 or 500 and the stock q-jet will be the larger one. some say 830cfm some say 800cfm some say 850cfm but either way with some simple mods they can and will support some large engines.
in '75 or '76 gm did have an altitude option in addition to the federal and calif emissions. there is also a p.o.e. on these to that you can modify to adjust part throttle a/f mixture.
quadrajets definitely seem to work better than most edelbrocks holleys and predators when doing something off-road (other than mud-bogs.) and no, I'm parting with mine. btw, holley does sell re-man'd caddy quadrajets.