Somewhere I read that Goodman package unit is certified for a mobile installation. I could be wrong but it would be worth your while to look it up on their web site on the the front of one of their installation manuals.
(reached over an opened a Goodman Products Catalog) Page 26 fro a PHKJ Series package unit and says "..and is approved for manufactured or modular homes."
Looks like most if not all their residential package units have the same wording.
"The American Republic will endure until the day Congress discovers it can bribe the public with the public's own money.
- Alexis de Toqueville, 1835