rear axle spline count

[81msw79]

is there any way to tell the spline count on gbody axles without physically popping one out? I have seen parts listings for both a 28 and 26 spline count.
I have an aftermarket auburn posi with Richmond 4.10 gears I would like to use that is a 26 spline unit but unsure what spline axles in the rear are.
car is an 83 Malibu wagon with a factory posi and 2.41 gears

 

[455'ed80Regal]

I think all g body cars had 26 spline axles. It is possible that the 88 models had the 28 spline axles but I'm not positive on that. If your rear end is original it will have 26 spline axles in it.