my swaybar is 1 and 5/16 but i think there are several variations.if you don't have a micrometer to measure the bar then take an open ended wrench and slip them one at a time over the bar until you have a tight fit and theres your sway bar size.
MT '90 lx was measured to be 1.3" exactly. A lot of people just use the 1 5/16" as it is 1.3125". Autozone/Checker may, may not list the 1.3" size or even the 1 5/16" size for a mustang. I had to specifically ask for 1 5/16". But you should definitely measure it before you go. If you don't have a micrometer, another easy way is to use a bendable tape measure (like a seamstress uses), and measure the circumference. Then divide by pi (3.141529), there's your diameter.
Another quick way to test would be to tighten a crescent wrench around the swaybar and use a tape measure to measure that distance.. But that's assuming you have a large enough crescent wrench.
First, sorry to bring this back from the dead, but I needed to check the size.
Besides that point, remember when we were all in 6th grade, asking, "when the hell am I ever gonna use Pi in my life???"
Well, Dromeda, THANK YOU FOR ANSWERING THAT QUESTION!!!!!
Kick ass.