I installed an Onan Marquis Gold 7000 in our then new Alfa fiver (2004) which had no gen prep. Having no gen prep is no big deal. The 5500 and 7000 have the same foot print. There was a guy in the park next to us which had a factory genny package in it along with the genny. I looked at it to get some ideas. After looking at the company's install he said "don't do it the way you see". Their install dropped the bottom of genny down below the bottom of the compartment about 1 1/4 inches. He had to have an Onan shop do warranty work on the genny, and the techs' made up new words getting the bottom of the genny high enough to clear the bottom of the cabinet door. I did some measuring and I could raise the Onan at least 1 1/4 inches above the bottom lip and still get it in the opening. I then took some inch square steel tubing, ground a slot the length of the tubing the width of the Onan mounting bolts. I made up some brackets to install these "rails" to the frame. This made it possible to slide the Onan in and out of the compartment if necessary just by loosening the 4 mounting bolts and removing the exhaust down pipe, and fuel line. I had a shop fabricate the sheet metal box for in the compartment. Remember that the bottom of this series of gennys require an open bottom. I used the West Marine website for a fuel tank, They have many plastic and metal tanks in all sorts of dimensions and gallons. The running of the wires for the remote start and hour meter into the fiver was simple. I did install a separate 12 volt start battery for the genny since the Onans have NO 12 volt charging circuit built into them. Don't ask how I found this out. The installation has worked very well as we still fulltime in the fiver. I just wish I could say the same thing about the Ono Onan. They are like an old woman, needing a lot of tender love and care. If I can be of more help just shoot me a PM.
