Hello!
Thank you for the reply. At first sight I said these planes were R models. But I didn't know F or L models had dorsal fillet. That's the reason why I'm not sure in this. Another question: There were any F or L models with dorsal fillet?
I apologize you for the 'brainstorming'.
There is a photograph in the softcover book, "P-40 Warhawk in Action #205," of a P-40F with a dorsal fillet. However, according to the caption only one "F" was configured thus, and the look of this fillet is different than that seen in the "K" model. Like Vince, my first thought was the one you are referring to is an "R," although the "In Action" book states that the "R" versions were originally P-40F airframes....which besides that one specimen had no dorsal fillet The book also indicates that the records regarding this model are conflicting, so perhaps it's possible that some "K" models had the perforated grills. You pose an interesting question....maybe there is no definite answer!
HTH,
Mark