what size torsions for a 69 dart for a little better handling?

1.03s minimum, for street, with a big sway bar and fancy-schmancy adjustable shocks,lol.
Well as to shocks IDK. I'm running HD Munroes,3-way adjustables,circa 1976. Hard to believe, I know! But they are almost new! They only have about 150,000 miles on. I guess they built stuff to last back then.
Or I just got old along with them, and together we're just waiting to die.

Don't forget tires and tire pressures; very important.