Some vehicles like the 3.0 Ranger come from the factory with their engine's timing set right on the edge of pinging in order to get the cleanest possible burn for emissions purposes. But as an engine gets a few miles on it, it carbons up and the carbon insulates the combustion chamber (or possibly raises the compression ratio) and makes it run hotter, and in an engine that has it's timing set to the max that extra combustion chamber heat then causes pinging.
Other than running a higher octane gasoline some suggested ways to deal with the problem is to reduce combustion chamber temps via a colder thermostat and spark plugs, or to retard the ignition. In the old days of distributor ignition it was very easy to advance or retard an engine's timing with a twist of the distributor, but with todays computer controlled ignition you need to program the computer in order to change the timing - and programming a computer via a chip or programmer is really no big deal and nothing to be afraid of.
But if you'd rather not alter your truck then by all means leave it stock and live with the pinging or else the added expense of running premium gasoline.
