Want it to handle like a new car!!!

Poly bushings for sure! The stock sway bar from the 73 is fine for right now but youll want to upgrade later. I would use at a min. Of 340/360 torsion bar, and upgrade to 1" bars down the road.
That being said if you want true modern type feel you need to change tue front and rear suspension like going the RMS front end and rear end street lynx kits. To run the rear end kit though you'll need to either use a 9"ford or 8 3/4 or Dana 60 rear end.
Talk to Abodyjoe if you want more info on the serums because he has them on his yellow dart.