IF it's one of the gazillions still on the road from mid '70-ish to late 90s-ish, you can BET THE RANCH that you have a mechanical failure INDIDE your steering wheel hub.
It'll be a broken pot-metal part, roughly shaped like a horseshoe - with the open end down.
That broken linkage fails to engage, via a pushrod, the ACTUAL ignition switch, which lies atop and centered above your steering column.
When you turn your ignition to the "on" position, your collection of dash-mounted "preflight check" lights come on, right? Look VERY closely (You might have to cup your hand to block out light.) for that tiny red "seatbelt warning" will NOT be on. Keep watching that "seatbelt" spot as you turn the key key to "start"............then turn it HARDER and "*dink*.
THERE'S that light! And darned if your truck doesn't start right up.
IF you own a Dremel tool and have no fear of using it, you can probably affect the repair yourself. You'll have to do a little judicious grinding away to make a new one fit without ABSOLUTELY "PERFECTING" your blue language skillset.
NAPA stocks that part in my small (population 15k) town, and sold me one just a very few years ago for a whopping ten bucks.
Protip: Do NOT......discard your damaged "horseshoe" until AFTER you get your new one in and is CONFIRMED to work reliably.
It won't hurt to have it in your pocket when you walk in to your favorite auto parts supplier.
Good luck. It ain't a HARD fix, but it IS kinda tedious. Beer served nicely as my helper.
geezer/geek/old fart-who-lives-in-a-cave-in-the-middle-of-a-central-Illinois-cornfield- Jimmj43