153088 was the 18th "real" F-4J(071 to 088 were parts of block 26 and 27), so thick wings, late engine exhausts, thick tires, all of those things would be on a model,,,,,,plus the B IR sensor under the nose, I don't see any notes about what might have been inside the fairing,,,,,,it might even have been still empty,,,,,,,the actual radome fit from a B to a J, and vice versa
the "it had it on there" part is still with us,,,,,,,but, the "why was it" part seems to have faded into history
the guy says testing,,,,that makes sense, but, it sure wasn't a prototype,,,,,,,,those 3 were still thin wing,,,,,,and the 18th production bird, not even close to a prototype