Of course, there is the stealth files that you need but I cannot help you with that, as I myself do not know where to obtain them.
EDIT: Ok I found the .ss, the pfi, and the dmi files (the stealth files) at xbox-sky. This is very useful as now you can download ANY xbox1 backup and convert it to a 360 iso file. I will try this out later and truly confirm this.
I should've probably said this earlier... You need xdvdmulleter 9.2, not the latest one as the latest one focuses on the xbox360 rather than xbox1. You also NEED daemon tools as that has true image mounting. I tried with poweriso, but isobuster did not detect it. This does work though, so no more searching for xbox to xbox 360 converted games (xbox360e). Make sure to check this first though: http://www.xbox.com/en-US/games/backwardco...tygameslist.htm