Mitch,
I believe the step you have uses heavy duty ball bearing drawer guides. I think they are rated for 200 pounds and are made by Accuride or Knape-Vogt. You will have to buy at least 1 set. I believe it takes a total of 2 pair. You will also have to drill out the rivets. The guides are not engineered to come apart so perhaps the best approach may be to replace both pair. Hope this helps, Fred