I suspect the rig was never intended to have a transfer switch. Many C class rigs (like my View) simply have a cord feeding the main breaker, and the generator has a 4x4 box with a TT30 receptacle in the cord compartment. You want generator power, you roll and store the cord in its compartment and plug it into the receptacle in the 4x4 box. You want shore power, you unplug from the generator receptacle and pull the cord out and plug into the pedestal. Idiot simple, just remember to always plug in the cord to the genny receptacle any time you stow the cord.
2007 Winnebago View 523H, 2006 Dodge (Daimler-Chrysler aka Mercedes) Sprinter 3500 chassis. Bought Sept 2015 with 18K miles, Prog Ind HW30C, Prog Dynamics PD4645, Chill Grille, Fanstatic Fan Ultrabreeze, PML/Yourcovers.com deep alum trans pan, Roadmaster sway bar