Upgrading a Fairly Stock Suspension

All good points made above. Most of your parts are 44 years old and worn out I would bet.

I replaced the front end with a rebuild kit from PST. I used the .920 torsion bars from Mopar Performance, and a six leaf set up from ESPO. Welded in some MP sub-frame connectors. Monroe gas-matic for shocks. You would be surprised what a difference this made. I will be adding a sway bar to the front soon.

It won't turn your Dart into a canyon carver, but it will give a good foundation to build off of.