Carter Thermoquad

You need to know:
a)the 4 digit part # stamped into the driver rear corner of the base,
b)the top casting #'s near the passenger rear vent stack.

For example, a 6138('72 340 4 spd carb) would have one of two top casting #'s:
6-2007 or 6-2080.

Also the primary butterflies have #s 2-310 or 2-315 for an oem 800 cfm or
2-314 for all oem 850 cfm carbs, David.