Carter Thermoquad

Hey Folks,

I need a little help identifying a carburetor. A guy has a Holley Remanufactured Carburetor, #64-1202 for sale. From what I can tell, this was originally ieither a:

1.) Carter Thermoquad 4972/4973 used on 1971 Chrysler 340 vehicles
Or a
2.) Carter Thermoquad 6138/6139 used on 1972 Chrysler 340 vehicles

Can anyone tell me what exactly I should be looking for if I want the 72' 1639 (AT) model? What is the difference between these models?

Thanks in advance for any help,