Torsion Bar Options

You don't want longer torsion bars, but larger diameter. Best deal I have found:

1.03" Torsion Bar - A Body

Mopar Performance makes some as well:

https://www.summitracing.com/parts/dcc-5249150/overview/

Sway bars, I suggest Hellwig:

https://www.summitracing.com/parts/hel-55914/overview/year/1964/make/plymouth/model/valiant


You may find that in addition to this fun performance stuff, the car needs basic stuff like a front end rebuild. I am doing the same thing to the same car myself right now. This, along with the mods, makes the cars handle pretty well....

Incidentally, what are you doing for brakes?