You're almost right Rob. The engine was available in different Horse Power, from 140hp to 180 hp. The first Cherokee version was the PA-28 Cherokee 150, with the 150 hp Lycoming 0-320-A2A, whilst the Cherokee 160 had the 160hp 0-320-D2A, and the 180 the 0-360-A2A, 180 hp.
The PA-28-140 was originally released as a two seat trainer, with the Lycoming 140hp 0-320-A2B engine, but was later offered as a four seater, as the PA28-140-4, in 1965, with the 0-320 uprated to 150hp.
Warrior and Warrior II had the 0-320-D3G, Archer/Archer II had the 0-360-A4M, and the Arrow had the IO-360-C1C at 200hp.
I got to fly the Arrow, and before that, a 1966 or 1967 Cherokee 140-4, which was then about 21 or 22 years old. And it definitely had four seats, as my girlfriend and I slept in the back of it !