I guess you don't need to wire up the reversing switch. Pretty neat though. I'm going to narrow down my advise to exclude everything except your last question. You seem to have the ignition and charging figured out. So the answer is yes regarding the picture you posted of the old starter, and as we said, it can operate on 12V if not stressed with long operation on a hard start situation. Attach the battery pos to it's stud, connect the appropriate linkage and spring as seen in Fig. 42 of the manual.................Done.
What a solenoid does: In the case of your starter(s), it slides the small pinion gear into the flywheel gear and almost simultaneously switches on the starter motor to begin cranking. There is an electromagnetic type where the mechanical pinion slide is done by sucking in a piston like plunger by an energized electromagnet to operate the slide lever and this also makes an electrical contact to spin the starter motor....which spins the truck motor.
The foot start type uses you as the solenoid. You push the pedal which, thru linkage/levers, slides the pinion into place and then presses the button to spin the starter motor....which spins the truck motor.
Both types have a return spring to retract the pinion away from the flywheel when you release the ignition switch/button or lift your foot.
