Rhoten - in the pass door there should be the same sort of triangular stiffening panel spotted inside w/ the holes and weld-nuts where the mirror mounts - if it's not there look in the drivers door to see what's needed - nobody repros them as they usually were in there even if the factory didn't put the mirror on - you also likely won't find it at a swap, as who'd bother to cut it free from a scrapped door?

easy enuff to fake if necessary
Bill
oh yeah - the accessory manual is talking of the extendable mirror that requires more than normal reinforcement