Ignition Switch and Key for a 65 Valiant

1.) Buy the extra switch.
2.) Buy a can of Lock-Ease, or a can of Mopar Rust Penetrant P/N 4318039AC
using either, spray into the key slot. Allow this lube to saturate and sit a couple hours.
This should allow the pins and springs to loosen and hopefully free your key.
I've seen this before, it usually happens because of dirt and other crap that ends up into the cylinder. Also the weight of keys acts as a lever and causes the tumblers to bind.
Stick your hand in your pockets, you'll be able to pull lint out, that crap will ride on your keys and over the years build up in the cylinders.
I may have a cylinder, but it will be un-coded and basically "open". I definitely have key blanks.