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?
