Any difference between say a '75 Dana 60 vs a 90's model rear axle

Looking for a Dana 60 truck housing to build for my Dart. I know the later models such as in the 90's have the speed sensor in the housing. Are the early and later gears the same, anything to watch for? Reason I ask is I have found a '98 model Dana 60. The earlier ones are harder to find around here.