Depends on your tire choice too. Unless you're going to run modern compound tires on 17 or 18" rims then there isn't much of a point going past even a 1.06" bar, you won't have enough grip to need those kind of wheel rates with any DOT legal street tires for a 15" rim. I ran my 1.12" bars with crappy 235/60/15's and 255/60/17's for awhile, the car was ridiculously loose, too much rate for the grip available and that was without sway bars. With 275/40/17's on it all the way around now the 1.12" bars work pretty well on the street.
Firm Feel offers E body bars in 1", 1.06", 1.12", and 1.18", but they also still have a tag on there about doing custom sizes/wheel rates. I know they've done 1.22" bars before. Hotchkis is selling 1.1" torsion bars for E-bodies not sure what the wheel rate is though, and P-S-T sells 1.03" bars. Bergman Auto Craft had 1.15" bars listed for E-bodies for awhile, but I don't see them on his page anymore. I think he was advertising those as a 300 lb/in rate, which is what I run on my Duster with Hotchkis Fox's. That car handles very well on the street. I have a set of 1.08's from a company called "SwayAway", although I don't think they're currently making any E-body bars.
Also keep in mind that for any of the larger bars you'll need better shocks, RCD Bilsteins, Hotchkis Fox's, etc unless your want your eyeballs rattled loose. I ran KYB's on my Challenger for a long time with the FFI 1.12" bars, when I swapped it over to RCD Bilsteins it was like a whole different car.