You might google around for similar situations. One unknown is your ceiling height, which has to be considered. Also, what amount of overspray (or underspray) is allowable? Just a quick thought - a width of 66 feet puts you in range of having a single row of four heads.
By the way, you can install sprinkler heads upside-down, and they will still work. A job like this could be done with low-angle rotor heads.