how the h*** do i know how many splines i've got?

[Danish88GT]

as the topic says!
My car is a 1988 Mustang GT belive i was told it was a HO? but arent all GT's?
getting a 4.10's and a new diff but splines splines!!!

 

[rsw007]

if its still stock then its 28splines

 

[Danish88GT]

if its still stock then its 28splines

THX! i'll keep shopping!