Help with leaf spring selection,

As far as tires go, I'm not really sure what you tell you. Selection for 15" rims pretty much drops to BFG T/A's and Cooper Cobra's once you go wider than a 225. I had a set of Falken Ziex's on my Duster when I was running cop rims, they were 225/60/15's. But once you go to a 235, 245 or larger all that's left for options are the T/A and Cobra's. They're "OK", but neither is designed for real performance handling.
I might look at the Mickey Thompson sportsman SR tires, they have all common 15" sizes.
How critical do you think having a rear sway bar is with my tire limitations?