Welcome to the forum
1991 Ranger 2.3l gets tach signal from the ICM(ignition control module) located on the front of the intake manifold.
ICM runs the spark system, check wires they often get frayed/loose
Crank position(CKP) sensor is the main timing sensor for the ICM and the computer, engine will not start without a stable signal from that sensor, so no, not the CKP sensor.
But the misfire could be a problem with the ICM which are known to have issues when older, so tach issue and misfire could be symptom of ICM problem.
Many auto parts stores have testers for these ICMs, you bring in that module and they can test it.
And read here: http://easyautodiagnostics.com/ford/...sensor-tests-1