The Cherokee Tribe is not specific on this, but reading between the lines suggests the Cruiser was a 2 seater, whereas the 140B is a 4 place. My 1966 model has rear seats, which apparently were an option that year.
In 1971, the rear seats were removed, and it became known as the FliteLiner
The following is an excerpt from The Cherokee Tribe:
The Cherokee 140 is the type of plane people get into fights over. Some argue it is a two-seat trainer. Others swear that it is a four-seat family plane. In fact, both are correct - up to a point.
Part of the problem may stem from the fact that Piper did not exactly know what to make of the plane. When first introduced in 1964 it was strictly a two- seat trainer, designed to replace the Colt and provide competition for the Cessna 150. To create the plane Piper stripped a Cherokee 150, including removing the rear seats, and then changed to a climb propeller and limited RPM to 2,450. The restrictions were short-lived, however. In 1965 the horsepower was increased-back to 150--and in 1966 Piper offered rear seats as an option. In 1969 the Cruiser model added luxury touches to the plane and, in fact, the rear seat became standard on that model. Sounds a lot like Piper was considering the plane a family plane, right?
So then, in 1971, the factory once again removed the rear seat and created the Flite Liner - a two-seat trainer. Well, no matter. The plane is what you want it to be. And most of the 140s in the field have had rear seats installed somewhere during their lives. The only problem is that the plane is a bit marginal in performance and sone pilots do not do the headwork required to stay out of trouble. Commonly, the scenario involves a pilot out-of- training for a long enough period to simply fly by "feel." He thinks i t is a sign of a newcomer to actually do weight-and- balance computations. But, if you fly a Cherokee 140 you had best get used to doing some computation. A 140, with all seats filled and with full fuel, is like a pet coral snake with a migraine headache. I wouldn't want to fool with it and neither would you.