O. K. the 66 Fleetline used a 2-1/2 inch hydralectric cylinder. Reason: smaller pump, cycle time would be similar to that of a 77 or 88 with the 3 inch cylinder. Enter the Super 66. Faster pump speed, more flow you might need to check a price book and see if both the 2-1/2 and the 3 inch were available. Remember stroke pin size, etc is the same for all of them.