More splines=more strength but also more diameter outside of splines. Splines are usually cut at the same size in axle to axle applications. Aftermarket custom axles are available for about anything you can think of, if you're willing to pay for them. Check your outer bearing and seal part numbers at Rock Auto to confirm the outer shaft is the same (I checked a while back and believe they are). If it's post 96, looking for a set of A body length 8-1/4 axles cut for later splines. Talk to Dr. Diff, Moser, or Strange. One overlooked advantage of aftermarket axles is they aren't tapered like factory axles, but cut to a beveled angle step down at the splines.