Tough question, wasted some time looking for an answer, but no luck. The blue box on the left is a Federal signal pa-20a, siren driver, but its missing the microphone for pa use. It's difficult since it may have been a prop. Law enforcement has always liked batwings (motorola) equipment, so I would expect to see a Motrac head along with the pa 20. Now given the timeframe, it could be a cb radio, but Billy Bob was some form of law enforcement, ranger, la fish and wildlife maybe. Given that, the long antennas, and the period, they would likely have operated commercial radios on low band, 39.9 mhz, mutual aid on 39.98. The radio microphone doesn't have the shape of motorola, GE, midland, Standard, Royce, RCA, lafayette, pace, cobra, or Johnson. Lettering on radio and microphone is not legible when zoomed in.
Curious to know why the interest, building a billy bob cv21?