66 Ford 9"

On my 1966 Ford F100 I have a 9 inch rear end that I am wanting to convert to disk brakes later or maybe and would like to know if I have a 28 spline or a 31 spline? Did they come in 31 spline back in 66? Reason I ask is because I have a WAR case and the hubs on the outside have the indention that goes in and I read a few sites that had pictures of the two different hubs and mine looks just like the 31 spline but then again the site said that some 28 splines look just like the 31's... Any help here please? If it's a 28 spline I am guessing no need to upgrade or what? The truck is my everyday driver and does have quite a bit of power going to it but then again not a drag truck or nothing. I want to put some kind of lockers in this thing later too.
Thanks a lot for any info, help, comments, and suggestions.

Shawn-

For anything but severe abuse, use what you've got, the splines won't matter.