What is the difference Mopar 8 3/4 to 9" ford?

Hey on the subject of the 8 3/4, I want to know if I have a housing that has a 489 case in an A body dart, and I get a hold of 742 posi unit, are there issues with the number of splines on the axles? I have seem talk about 30 & 35 spline axles.

I would need to pull an axle to see what I have now, but I think stock are 30 correct?

Thanks!