No, not talking about the venerable compact/midisize SUV of the modern day. Back in the day, Explorer was a trim level of the fullsize Ford pickup line. It was available with all body styles and all weight ranges. However, the Explorer package was most prevalent on the F100 and F150 platforms. This was more of a value package, similar to what manufacturers like to market today.
Of course, the Explorer followed the updates of the entire light duty Ford truck line. The 1973-1977 models had a similar appearance, as did the 1978-1979, and the 1980-up.
There were three levels of Explorer initially. First was Explorer Package A, or baseline, if you will. This included unique exterior and interior colors (changed per year), color-keyed floor mats, chrome bumper guards, bumper rub strips, bright mirrors, chrome windshield molding, bright wheel covers, tape striping, badges, and bright bed rails.
Next came Explorer Package B, which included all of A plus power steering and cruise control. The third was Explorer Package C, which included all of A/B plus air conditioning and tinted glass.
In 1978, the bright bed rails were dropped from the package, but still could be ordered a-la-carte through the dealer. A fourth Explorer group was sold starting this year and was called what else, but Package D. This added a white camper top and was probably the only factory-supplied pickup cap ever.
The Explorer package was around until the late 1980s, then dropped when the model name became the SUV.