Finally got around to looking at my Mack books.
Yes, it is a CF 600 series. Not sure on the sub-series but most likely a CF 611 as it seems to be the most popular series for the Aerialscopes. Sub-series was based on the engines:
608 = 707C Gas
611 = E6-260 Diesel
685 = EM6-237 Diesel
686 = EM6-285 Diesel
The 700 series had a V-8 Diesel:
795 = ENDT865-325 Diesel