How do the body lines on the door line up before closing, low I'd guess? Is the striker post cracked, in other words can it be moving around. A bodies are notorious for the striker cracking out. How does the door to fender gap look, even or not? The door is fairly easy to adjust, but you'll need a floor jack or two people to it.

Also on the pic of the key in the lock, the key is upside down, on Chryslers the long part goes on the bottom, keyed (grooved) part goes up.

I HIGHLY recommend getting a 1968 Dodge service manual, as it will show and explain how to make everything function as new. Buy the book not the CD, unless you can take your laptop with you.