According to the spec sheet on my 5500, the original tires were an F78x14 - a previous owner put new tires on, ST205/75 R14's. Although they come very close to the wheel skirt on the outside (1/2"), there is no evidence of any rubbing on the wheel well - about 4-5" clearance from the top of the tire. My suspension is the familiar torsion arm (just like the 1300). Should be no reason you cannot use 14 inch wheels that I am aware of - just make sure you get wheels/tires of at least 1760lbs capacity each (load range C for the tires).
I did find however that the wheel is a 5 bolt 4 1/2" bolt circle (just freshly measured). Most 14" replacement wheels I have seen (although I must admit not looking too hard) were 5 bolt 5 1/2" bolt circle. Given all the other differences we have found between individual 5500's, I would take careful measurement of your own prior to buying any new rims - they could well be different too! (Incidently, mine also uses wheel bolts from the outside into the hub, like some European cars - not studs from the hub with nuts on the outside like most North American vehicles).