What are "L" and "Y" codes for a 350???

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I am trying to replace the choke thermostat on my 71' Cheyenne and am having a heck of a time with finding the right one. The one it has in it now it stamped with a "232-3" on the top of the spring, but I can't reference that anywhere.

I've narrowed it down to 2 possible units. One calls out a number for a 5.7L with a "Y" or "L" engine code, and the other for just a 5.7L. My truck has the stock 350 with the stock 4bbl Quadrajet all original to the truck. I can't find one in the parts stores, and the ones I see on eBay for a 350 4bbl seem to exclude a 1971 truck.

Can anyone please clue me in on the "L" and "Y" codes? I think this will solve my problem.

Thanks in advance.