Way back in high school I drove an old Studebaker with manual steering. It was a fairly small car but had the V8, which is a much heavier engine than the slant six. It was also very hard to steer.
Couldn't figure out how so many old ladies in town could drive their big Buicks, etc. every day when their cars didn't have power steering either.
I found out after doing a lube job on the front end. The difference was like night and day. As long as the car wasn't sitting completely still, I could steer it with very little effort. It wasn't like having power steering, but man what a difference.
If your Dart hasn't had a complete lube job recently, give it a try and see if that helps. It should make it easier to drive and would improve more than just the steering effort. That was another part of regular maintenance that modern cars don't need, and is easy to forget about.