i want to put a locker in my 1992 f150 but the company that i am buying from needs to know whether the axle has 28 splines or 31 splines.......i'm clueless on that one. 3.55 gears and axle code is 19. well if i could get an answer or be directed to where i could find a solution to this boggle, it would be aprecciated. thanks.

 

31 spline. If you told the it was for an F150, they should have known that.