Ian,
Heres what I've gleaned from factory photos. The 42 pickup was fitted with the 1941 car caps (as was the 41 pickup) then after the war, the 45-46 pickup was fitted with the 42 car caps, the 47 pickup used the 1946 car cap. Your cap was fitted to 48-56 F1/F100, I have seen 48 F1's fitted with the 46 car caps in factory pics.
Going from that if yours is a 1943 (I'm unsure on this as from what I've found out so far from sniffing out info on these orphan year pickups) there was no 1/2 tons made after sometime in 1942, started up again late 1945. Saying that, compared to all other years of pickups (except maybe 38-39) there is precious little info out there!
Any how, if yours is a 43, it would have either the same as the 42 had (the 1941 car cap) or, a slim or, the 1942 car cap. Though I've not seen this in any Ford photos.
Martin.