John,
Thanks for your comments.
After speaking with Prevost personnel I am confident in the use of the replacement bags they recommend (151). Having thoughly examined the IFS components for wear it appears the only issue is with the bushings in one of the upper a-arms, I am pulling both upper arms and replacing all bushings. As the chafing is being done by the upper spring housing which is stationary and all the associated components are in excellent condition I feel it is highly probable that there was some poor engineering by C.C.. My concern would be with buses similar to mine. I believe other owners of the same era would be well served to check their steer axle bags. It is fairly easy to determine if they are Firestone bags, if they find them they should be examined. Although I felt replacing the bags at ten years (my bus is registered as a 2002 but the chassis is 2001) was a bit overly cautious I am a believer now.