86 Chevrolet 4x4 lug nut size??

[bgarner1983]

Hey guys I bought some more wheels for my truck and have to buy a different style lug nut for them because the ones on the truck will not fit the new wheels. My question is what size lugnuts are suppose to go on this truck? I pulled one off when i was checking the wheels that was stripped and it says it is a 12m 1.50 but I can't find anywhere saying what size they suppose to be. Figured you guru's could help me out on this. Thanks!