The info on the YF Carburetors was taken right off the A.E.A Henry J tune up sheet for the 1951 four cylinder model. I just now pulled out the Henry J Service Standard guide which was published by Kaiser-Frazer. Page 9 lists carburetor for the four cylinder as "Down Draft, Single, Carter 820S, SA or SB." The thing to keep in mind if you're comparing it to one that was removed is that these cars/engines are 50+ years old and you can't be certain that things have not already been replaced. In fact, it is likely they have been replaced and often times people were forced to use what they could find instead of what was specified in the factory literature. Page 27 of the factory Henry J parts manual also lists the carburetor as "Carter YF820S, 820SA, or 820SB." I don't know for sure, but it is certainly possible that the F-head and L-head used the same carb. I checked the 1955 edition of "Motors Auto Repair" and it lists same for 4 cyl Henry J. It also lists "YF" types for all Willys vehicles but it does not distinguish between L-head and F-head so I'd say there's a good possibility that it's the same. I also checked Rudy's KF Parts catalog which lists simply "YF" but he sells them and knows the parts/cars quite well. You may want to call him. His number is "Rudy's KF Parts" phone 1-760-789-3608. Good luck and let us know what you find.
