A sway bar only can act as travel limiter on one wheel at a time. If both wheels are off the ground, then there is no effect. In other words, it's unlikely that the lack of a sway bar contributed to your misfortune with the shock.
As to your primary question, jacking up the truck to let the wheels droop fully would be the way to measure for the limit strap. It might be tricky calculating the length you should have when you need to consider the mounting hardware. My Superlift came with the limit strap, so I've never had to do the figuring. Maybe a call to ORW or 4WP or some other retailer would be helpful.
EDIT: just read your other thread; the maxed T-bars are the probable cause of the shock damage, so limit straps would help.
2004 Ranger FX4 Level II, Superlift 4" lift, Bama program, BFG 32x11.50x15 tires, Undercover, Rancho RS9000X shocks.
Last edited by Reddog99; 07-06-2010 at 08:37 PM.