70s Power Wagon Ignition switch info needed !!

Greetings and Salutations
Have a new problem electrical of course truck sets a few days and it will turn over but not crank or fire !
Put battery charger on and it fires instantly - replaced battery but wasn't issue , and noticed while trying to start it WITHOUT battery charger hooked up when u release ignition switch and click to off motor turns a little the opposite direction!!!!
Trucks is a 76 model so went ahead and bought a new ignition switch but upon opening box unit just inserts into column nothing electrical visible on it but it's bought and going in ASAP any thoughts on main issue thanks.
You say it will turn over, but, not crank......isn't that the same thing? Have you measured the voltage to the coil/ballast/ECU while cranking?