Not sure about the 1998 year model, but we have a 2000 Chieftain that we have been very pleased with. Ours is on the Ford F53 chassis. Seems I heard somewhere along the line that some of the motorhomes had a narrow width and caused some handling issues, then in the late 90's they went to a wider chassis which helped.
If you have any questions, let me know and I will try to answer them. What ever you buy, drive it, inspect it and ask a lot of questions!
2001 Monaco Dynasty
2004 Jeep Liberty