This picture might be somewhat helpful, I haven't found any other information on Adams ambulances but the picture is dated 1984.
https://lacaa.net/about/ This is the website it came from, it might also be helpful but that was the only photo it had for the 80s-90s timeframe.
It also has some photos of the Cadillac style ambulances that made it into the late 70s and early 80s.
https://aaoc.net/about-us/ couple of good pictures here including a what looks to be a CARE Ford E-series with a larger box. (Although orange county is probably out of the way for this mod)