A #226 throttle plate was used in early front and rear carburetors. These had a tendency to stick and a Chrysler Technical Bulletin was issued to change to a #199 plate after date code 3149. I got New Holley plates (p/n 9R199V) from Holley Technical Support for my carbs.
The hole size in the plates is very dependent on the engine specs (CR, cam etc). You want the center carb plates to be just uncovering the transfer slot at idle. This will give you adjustability on the idle mixture screws.
It is a real trial and error to get it right because you have to remove the center carb to see where the plates are positioned.
Jim
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