First factory 6 pack

Of those choices in the poll, J2 is the right answer, but I think the caddy might have had triple two barrels in 56. If you talking three carbs, you have to go further back....
The Olds predated the 348 by a year, the 406 and 421 by five. (But there was a tripower389 Pontiac by 58, and a 352/390 Ford somewhere around that time)