What size/type fixings should secure it to the body? I have three holes just under 5mm diameter, tried what looks like the correct size self tapper but they won't hold so clearly too small.
I dont want to nut & bolt it as its a syncro and it will be difficult, going on impossible with the tank in place.
I have nothing in stock bigger and short enough to do the job

1985 Oettinger 3.2 Caravelle RHD syncro twin slider. SA Microbus bumpers, duplex winch system, ARC 7X15 period alloys