This is a non-IRST chin (radome) pod for early F-4B's, specifically for the Tamiya kit. This pod/fairing was fitted to early F-4B's before and after the short "era" of the IRST system. While in development during the F4H /F4H-1 phase, the first regular F-4B off the production line were not yet fitted with the IRST pod until ca. 1962. Instead, they were fitted with this early, empty pod under the radome.

However, the IRST system wasn't working as well as anticipated and it was deleted soon, to be replaced again with either this short, empty pod, or later on with the pod in the Tamiya kit which is the late type, having longer forward fairing. This pod has the shorter, early forward fairing, seen on many early operational F-4B's. Please check your reference photo(s). A simple one-piece like-for-like resin replacement part.