[qcj]

Upgrade from 315/80R22.5 to Michelin XZA 365/70R22.5 per Newell:

Coaches 443 (1997) - 696 (2004) EXCEPT 671, 681 and 685 should only require new wheels and tires.
Coaches 671, 681, 685 and 697-775 require new wheels and tires, wheel hubs and fender modifications. (Steerable tags)
Coaches 776-1229 require new wheels and tires, wheel hubs and body modifications. (P2000i body style)
Coaches beginning with 1230 were built with the 365/70R22.5 tires as standard equipment.

So to answer the question asked, a 1998 would not require new hubs/spindles.  Just buy new wheels and tires.  

Tom should be able to give a pretty good estimate of the cost since he replaced his front wheels and tires to upgrade to the 365/70's a few years ago.

Michael, two months ago they told me $10,000.  Lot of money for two tires and wheels?  I believe they have to change out lug bolts also.  Still seems like a lot of money.