Are they for seat belt anchors that were for some reason changed? Your signature says you have a ‘93 but your text says ‘95; if the seats were modernized or something, the belting for 3 points may be different than for 2 point ones. I have no idea what was originally provided those years, and the brochures only say that seat belts are standard without elucidating.
You indicate you saw they were forward of the fuel tank, implying that you’ve looked underneath the coach and perhaps saw either nothing (indicating they are wood screws), or you saw through-floor machine screw ends with nuts with nothing attached (indicating they no longer perform their factory intent, and serve only now to plug holes). The hollow sound seems to say there’s no frame member directly underneath.
Joel