This looks very similar to the one I am running on my 66 GT350. Drove it to SAAC 35, 2000 mile round trip. I got about 18 miles to the gallon. The 3.00:1 gear set for the trip made the difference. Very fun. The original carbs would be Holley LIST 3360 and 3361. The carbs on your set up look like two secondary carbs with the missing butterfly. Please tell me the numbers on your carbs. I have looked at least four or five sets of original carbs and they all seem to be dated near June 1966.
Best of luck
Cory