Complex sentence: All units mostly replaced Orion Vs 1001-1014 and 1101-1129, except 801-822 which replaced Gillig Phantom Suburban units 501-522.
Split into simpler sentences: All units mostly replaced Orion Vs 1001-1014 and 1101-1129. Except 801-822 which replaced Gillig Phantom Suburban units 501-522.