We have the Firestone Ride-Rite bags on both front and rear suspension of our 2000 coach on the f53 chassis. Unless there has been some major change in the f53 front suspension, it would appear the representative providing you with such information is in error. As others mentioned I would talk to someone else.
Just went to their website and found the kit to fit your coach:
Check it out Here:
http://www.firestoneip.com/RideRite/kitSearch.aspxBest of luck and safe travels....
A side Note: Firestone's website reflects the the kit is for 16,000 & 18,000 GVWR 1999-2007 chassis. However the same air springs were used on our coach with the 20,500 GVWR chassis.