66 Coment Cyclone GT rear axle splines?
 

I have a '66 Comet Cyclone GT with a 390, 4 speed top loader, and 4.11 posi rear end. I'm looking to change to a different rear axle ratio in the 3.00 to 3.25 range to slow down the rpms at highway speed. Should this car have 28 spline rear axles? Thanks, GAJIM