It's 50+ years old. Quite frankly 64k or 164k doesn't matter much to me. Unless they state specific parts have been replaced I am already assuming steering, suspension, brakes, and/or the engine may need some work. I'm more concerned about rust, structure, and body on something like this.
Kevin I'm the opposite. After a price the next thing I look at is the mileage. Right now I'm looking for an older full sized van or decent pick up truck. Anything with over 100,000 miles I don't even check. I'd rather have a rusty 75,000 mile vehicle than a shiny 175,000 mile one. Of course I'm looking for something to move with not show. Then again, if it's a decent collectable car it is the body and chassis I look at. Most likely even at 60,000 everything mechanical has or will need replaced.
My '96 Chevy K1500 is just what you need, Cat! Just turned over 75k miles. And she's got rust aplenty! If I could get $1,000 for it, I'd be doing well. Too bad I'm about the same distance from Illinois as you are - in the wrong direction. As for the Rambler, the seller would have been better off starting the bidding lower to see how high it would have run up. Starting at $6k looked like high expectations.
Rust makes them lighter and it will match the other Illinois trucks. Check the antifreeze and put on some snow tires. We can meet some place in Indiana to wheel and deal. I'll start the bidding at $750.