The fourth generation of this truck really had two sub-generations: before and after 1965. 1965 was an important year for this truck. A 4 door crew cab was available for the first time, and a refresh of the powertrain pushed horsepower north of 200. Coil springs were put on the twin I-beam front suspension. It was also the first year the name "Ranger" was used on a Ford truck. It was a styling package on the F series, although it would later become its own model line of compact trucks.
Engines on this generation of the truck ranged from a straight 6 making 137 horsepower (used from 1961 to 1964) all the way up to a FE V8 making 208 horsepower. The 4.9 liter straight 6 introduced in 1965 was such a dependable engine that was used in Ford vehicles until 1996.
These trucks are becoming more popular with collectors. Some have survived the decades, while others were once abandoned and are just now being restored. You can find them hidden in the used car classified listings, or you just look at the listings on eBay. There will always be several listings there, along with lots of parts if you are already restoring one.