Re: Replacing the front door
Drop in doors for RV's are simple, just adjust your opening and rivet it in.
As far as hinges, you can spot weld the pin in place, also they make higher security hinges that are pressed together, the pin can't be knocked out.
I wouldn't really worry about the hinges if you use a house door, more than likely anyone who wants into a converted schoolbus will be an amateur thief and will prob just break a window.
If you want to SECURE it, for instance if it will be alone on a remote hunting property, install 16 gauge "hurricane shutters" with a top piano hinge and a bottom hi security hasp and padlock, same for the door, just use a metal security door or a piece of sheet with side hinges.