[CJE]

Considering the different manuals and handbooks available on the F4U-1, none of them specify the variant "A", while the variants "C" and "D" are duly recorded:

Flight Operating Handbook - F4U-1, 1C, 1D; FG-1, 1D; AN # 01-45HA-1 3/15/45 revised 12/1/52;

Maintenance Manual - F4U-1/-1C/-1D/F3A-1/FG-1/FG-1D (AN 01-45HA-2);

Even this:
Illustrated Parts Catalog - F4U-1/-1C/-1D/F3A-1/FG-1/FG-1D (AN 01-45HA-4).

To name but a few.