"Anti-roll" (not sway) bars can be a variety of diameters, depending on what handling characteristics you're looking for. The thicker the bar, the more positive the handling will be in turns, but there will be more harshness of the ride with a thicker bar as it will transmit more road feel to the frame when only one wheel hits a bump. Generally, rear bars need to be slightly smaller diameter than front ones especially on a pickup, as too big a rear bar will cause the rear end to hop around in a turn with a rough surface because of less weight in the bed when running unloaded. That's particularly true of a Cowboy Cadillac that never hauls anything heavier than a set of golf clubs or a Yeti cooler for tailgating.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!