Okay, did some digging through the factory Packard service manual.
According to the manual, the 2631 chassis came with a Carter WCFB-985-S carburetor.
It goes on to list both the Primary (Front), and Secondary (Rear) venturi sizes as 1 1/16"
If you look at the original picture I posted, you can see the 1 1/16" symbols on both the front and rear.
I've attached a picture of the manual for reference.
Regarding the sleeves - My neighbor (old hotrodder) knew what they were. He said they're usually referred to as venturi restrictors, venturi sleeves, or venturi chokes.
He went on to say that they shim down the secondary throats, giving sharper vacuum signal and hence better throttle response.
I know the carb was rebuilt at least a few times (receipts in glovebox) over the years. I'm assuming one of the rebuilders added these at one point.
Anyway, I think I'll leave 'em in for now and see what happens.
Thank you all for the help.
20210302_195822dfdf.jpg (240.76 KB)
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