Check out www.progressivesuspension.com. They have an application finder on their site. Most of their shocks are sold without springs, but I highly recommend replacing the springs with the springs they advise for your weight range. The 26 year old springs that are on the shocks you want to replace are sure to be sacked.
If money is no object, check out www.worksperformance.com, they'll custom make a pair of shocks based on the weight of the bike and your weight.
One more tip, don't neglect the forks. If you are going to renew the rear suspension, you should at least refresh the front. New springs, seals and fork oil should be the very least you do for the forks.