Have you tried the Onan/Cummins website? Perhaps they have something there, or an 800 number for info?
Also, what about checking with Excel?
Not familiar with that model, but my 5500 Onan Marquis requires an exhaust opening for the cooling air to exit, and space to change out the oil filter, all thru the trailer floor.
On edit: If you go to the Onan power generation site and register, you will be able to look up some technical drawings, but you will need more than the model number you list above--there is a more detailed number somewhere on the unit. And, check yellow pages for nearest Cummins dealer--they usually are very helpful even to non-commercial guys.
'05 36TK3 Mobile Suites
'10 F450 new to me
'09 F450 Lariat 4x4--died