Gary, serpentine belt idler pulleys seem to show up frquently as a Technical Service Bulletin (TSB) items, so if you check online or with a dealer you're more likely to get the latest redesign, if applicable.
I did most of the mods and service on our Mustang Cobra track car and an '85 Toyota MR2, but the daily drivers are mostly serviced at the dealer. Road grime doesn't inspire me, plus my 50+ year old knees now have a problem with concrete floors.