Hi,
look at the axle tube ends where the bearings reside, they should be a little larger than the axle tube see the attached photo, for-warning the axle bearings are unique to the GS and sportwagons
as far as I am aware the axles them selves are the same as other A bodies
also check the lenght as not sure off hand but sure you should be able to find this out as 64 and 65 are narrower than later 66 and up
Jim