Most of the time, a stud with lefthand threads will have a big "L" stamped on the end of the stud. You should also be able to inspect the end of the thread sticking out of the lug nut and follow the helix in a CCW direction. I don't recall any of the light duty Chevy trucks with LH threads on the driver's side, but Dodge, Studebaker, and a few others definitely were set up that way. Sometimes it's necessary to use a little heat and some penetrating oil like KROIL to loosen up the really stubborn ones.
Jerry
