Tottenville, in Staten Island, is the southernmost and most distant firehouse from the ferry (Manhattan) and Verrazano Narrows bridge (Brooklyn). In the early 1970's, it was isolated with most SI development on the North shore. There were a lot of older large private dwellings, schools, orphanages ("Godfather" baptism scene), churches, some factories, a large shoreline with barges and marine buildings and large wooded areas prone to difficult brush fires.
As I recall, Combo 151, called "The Combo" by SI dispatchers, was staffed each shift with 1 Capt, 4 FF on the engine section and 5 FF on the truck section. They responded as one unit - The Combo. The purpose, I believe, was to save the City a few bucks by eliminating the LT slot in the truck. It did operate with a captain each tour. The unique units selected for combo designation were engine/trucks housed together, usually responded to all boxes together, did not relocate and were not assigned on many multiple alarms to pull them out of their district.
Engine 151 and Ladder 76 were not busy companies, but when they got something, they operated on their own for quite a while. E 164/L84 (2nd due) were almost 4 miles away from the Tottenville firehouse, E162/L82/Bn 23 were about 6 or 7 miles away. The fire location could also be further away than the Combo's firehouse, so the chief and the 3rd due engine (E 162, if assigned) could have a 10 minute run or longer. Engine 167 and Engine 168 did not exist back then.
The combined unit concept did not work well because it always took "both sections" to do any run. A simple engine job took the "truck" section out of service, too. You had one officer leading two sections or engine/truck functions at a job. Tough to do. This was not a popular concept. I do not remember a 2 color helmet but I think their helmet front-pieces might have been red and black.
Additional note - I think the most famous fire fought by Combo 151 was the Mt Loretto (orphanage) church fire, 1973, which was the scene of the famous climax baptism and revenge scenes of the original "Godfather " movie. Church of St. Joachim and St. Anne was the name of the church. It was a 3 or 4 alarm job. The Combo was first due. The source of the fire was in the boiler room. The church was almost a total loss, except for the front, which still stands today.
The fire happened soon after the opening of the first "Godfather" movie. Maybe someone didn't like the movie. "Leave the gun, take the cannolis".
http://www.nypl.org/blogs/2009/06/05/mount-loretto-staten-island-ny
NOTE - Mt Loretto fire was in 1973 - the year before E 151 and L 76 became a Combo.