Before the F-16s became the drone target conversion of choice for the USAF, the F-4 was the jet. The contract for conversion was run by Tracor which ultimately ended up being part of BAE Systems at the time I saw these jets.  They did the conversion program at Mojave Airport in California.  We were a bit of a distance from the ramp where they were parked but it was early in the day and the heat haze was not yet a problem so a long shot was feasible.  Looking at these, I think they were both RF-4C jets that had either been converted or were about to be.