This is a 6515, same bore/venturi specs as the '70-72 HP carbs.
FYI, list number 6515 is a factory replacement designed as a bolt-on replacement for all these OE 1 ¾” secondary bore 4160s from ’70 thru ‘72. Includes all possible features of the original list numbers, with some later improvements like an o-ringed transfer tube for the accelerator pump passage, metering block to main body and the later more conventional idle circuit design.
BTW, If you are looking for a CFM rating for these carbs, you won’t find a accurate published number anywhere. The commonly published number is 600cfm, even documents from Holley from back then use this number. These carbs are more like 725cfm if you do the dimensional math using data points from current Holley spec sheets.