1964 Dart Owner - In Over My Head

Ah, a Slant-6, that's the best kind. :-) Tune-up parts and technique suggestions in this thread, and carburetor operation and repair manuals and links to training movies and carb repair/modification threads are posted here for free download. Your PCV hookup looks correct, but you'll want to make sure it's actually working -- pull the PCV valve off the rear of the valve cover with the engine idling and put your thumb over the inside end of it. Does your thumb get immediately and firmly sucked onto the end of the valve? If so, great. If not, you've got some maintenance to do.

Extra-stiff rear springs might reduce the tire/car contact, but probably won't eliminate it all the way until you've made the springs so stiff that the car is unpleasant and/or unsafe to drive.

Now with links, it is very much worth your while to get the good gaskets for the manifolds-to-head, intake-to-exhaust, and manifold-to-headpipe junctions to seal up the exhaust leaks.

The previous owner's air cleaner modification (cutting off the body of the lid that used to drop down over the sides of the air cleaner element) was not as clever as he thought. All it does is make the engine louder—without any (other) benefit.

The single-pot brake master cylinder speaks of original (underspecified) brakes. Hit that last link in my previous post in this thread sooner than later.