Post pictures of your pods, and see 679012 and other early FHCs with Mark V pods. They are a little bit different from normal XK120 pods.
At this point we have no evidence that the factory put turn signals on OTS until Sept '52, so the idea of owner mods is more likely. In Illinois, turn signals were required on new cars in 1954, and some other states required them around that time, so possibly owners of earlier cars might have wanted them and had them installed by dealers or body shops.
Careful examination of the archaeology of your cars and comparison with known factory parts and methods seems warranted here.