What concerns should I have to keep the rear suspension in good shape? Right now I have no driving or tire wear issues however it appears the rear-end is not centered in the chassis correctly. Is there something that wears out and needs attention? The right side wheel/tire appears closer to the fender than the left by about 3/4" or so! I've crawled under the car and did not see any leaks or anything that appeared to be out of place.

Thanks to all replies!

The differential is bolted to the chassis. Unless the bushings in the "batwing" mount are shot, there's no way for it to be out of position.
The tires/wheels are located by means of the half-shafts themselves, and the strut rods. What your issue is is most likely an alignment problem. If one side has more positive camber than the other, the top of the tire will be leaning into the car, away from the fender. This could account for the difference side/side. If you stand directly behind the car, you might be able to see the tire leaning in on that one side.
Might just need an alignment, but you also need the bushings in the suspension components checked carefully first.

Thanks for the reply, I will follow through with your suggestions. I never considered it to be an alignment issue.