See if someone has pictures of the ambulance when it was new, or if some of the Fire Dept. members can recall lighting configuration.
I don't think the lights on your ambulance had the chrome bezels. Those would have most likely been a surface mount Unity sealed beam light with the white extrusions used to create the tunnel light. (The 1976 Ambulance pictured was probably from another manufacturer.) Siren speakers or a small light bar with center speaker grill was mounted above the crew cab.
Were there holes for roof-mounted beacons? Since rear roof warning lights appear to be missing, search for bracket holes at the rear and front of the top. Model 184 or Model 14 roof beacons were common on the front, or tear drop lights or Unity flood lights on the roof cap at the rear. The mounting holes or pictures of the original vehicle might show how it was configuered.
Most of the era flashing light's were a Weldon or similar red plastic light face and diffuser, with a GE sealed beam and metal lamp cage. The lighthead was flush with the roof cap, but the lamp could be tilted a little in the light cage to direct the light beam. That was the reason for the large recessed holes. (A strobe conversion kit was introduced later, so the same light heads could be used.) The amber OEM front signal lamps are missing in the photo, and there don't appear to be warning lights in or behind the grill.
The rear signal lamps appear to be Grote tail lights like those used on recreational vehicles in the 1970's. We used to glue in some polished aluminum foil into the back as a reflector, since these tail lights just had a white plastic backing