Torsion bar knowledge

Ok guys, so heres the deal, i am a newbie to the wonderful world of chrysler. ( i was a gm guy in a prior life) i am learning a lot very quickly about a-bodys, but would like some expert advice. I recently purchased a cherry 75 gold duster that belonged to an grandmother. She bought it new in 75. It has 93,000 miles. I need to replace the torsion bars as they are worn plum out. I have looked around online and classic industrie offers 3 diffrent sizes. ( i think .081, .090, and 1.013 or so)
this will be a daily driver car that i might take out once in a while to the local 1/8 mile track. What size bar should i get to retain a stock ride height and a firm ride?
Any help would be greatly appreciated.