If you bought it from the Palm Harbor manufacturer in Casa Grande and it was delivered to Seligman new then it is most likely a manufactured home. If the axles are still on it as if it could be moved then it is a mobile home. A home 16 feet wide would require a DOT permit to move, thus not a mobile home.
In order to get a FHA or HUD loan on it you will need a foundation certification done by an engineer. That may or may not require modification to the existing foundation.
You may also want to verify that the roof is structurally capable of holding the weight of the panels. Manufactured homes that old are not designed to carry more than asphalt shingles.
If you can get a loan without taking equity out of your house do it. Better to lose the panels if you can't repay than lose the house.