I don't know a lot about Itascas, but if it is on a Ford F53 chassis then yes, you do.
I was luckier than I knew on mine. I loosened the filler hoses, undid the straps and let mine down with a motorcycle jack. Other folks have had leveling jacks, welded crossmembers, and who knows what in their way. Just because they are on the same chassis sure doesn't mean they are all the same.