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Hey, I am restoring a 66 GTO for my dad. It is a 389 4bbl Automatic with a date correct engine. When I purchased the car the carburetor and intake manifold were sitting on the engine and not bolted down. This raised questions for me as there were over 30 gtos in the barn that I bought mine from, so I was worried it wasn't correct. While investigating my carburetor it had a pink tag on it reading “CO PC 4248s” which I was told was incorrect for a 389 and it was for a 326. I was told I needed a 4034S. I ordered a rebuilt 4034S and when it arrived it looks identical to the carburetor I had. I am looking to find out what the difference is between the 4248s and 4034s, and what carburetors I have in front of me? Attached are photos of the carb that came with the car and the one I just received, along with the tag and photo of the car. Thanks in advance for all the help.
 

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4248S shows up as a 1967 285HP 326/automatic on the Firebird & Tempest/GTO having A.I.R.(Air Injection passages for the exhaust - Smog equipped engines).

4034S shows up as a 1966 335HP, Block Code YS, 389/automatic Tempest/GTO, non A.I.R. engine. Also used on 1966 B-Body 389/automatic cars.

That said, the carbs are engine/trans specific, with and without A.I.R. passages, and most likely fitted with application specific internals such as jets, step-up springs/metering rods, and idle-air bleeds.
 

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4248S shows up as a 1967 285HP 326/automatic on the Firebird & Tempest/GTO having A.I.R.(Air Injection passages for the exhaust - Smog equipped engines).

4034S shows up as a 1966 335HP, Block Code YS, 389/automatic Tempest/GTO, non A.I.R. engine. Also used on 1966 B-Body 389/automatic cars.

That said, the carbs are engine/trans specific, with and without A.I.R. passages, and most likely fitted with application specific internals such as jets, step-up springs/metering rods, and idle-air bleeds.
Hey thanks for the reply, are you saying that the 4034s is correct and it is ok that they look the same and the difference between them is internal?
 
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