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

building a 69 dart for a friend, its a /6 car that will be getting a 6.1 third gem hemi. keeping stock style suspension but wanting it to handle better without beating his brains out. we will be doing f/r sway bars and the full us cartool frame stiffening/minitub/spring relocate, ot sure what diameter torsions to get, what do you guys reccomend? thanks guys!
Well, without knowing exactly what the car will weigh when completed, it is a bit of a guessing game on our part. And We all find different levels of "stiff" acceptable, You did say
"a little better handling" in the heading, but that's not askin' for much w/the stock /6 bars, lol! Certainly no less than the .890" stock BB bars, but guessing at the weight, .920" &
up to your comfort level. If the roads in your area are condition "challenged", You may want to err on the softer side, whatever you choose good shocks are a must.