Others may have a different story, but on my '90 Westy, those bolts hanging under the
floor on the right side were NYLON, not steel, just fillers. The nuts were there okay,
welded to the steel floor, but I had to pop the plywood floor loose, raise it and
reach in and thread the proper bolts in.
The PO of my '88 Westy not only hung the tank from the nylon bolts, but had no
regulator on the second tank, running high pressure gas over to the other side where
it tee'd in up-stream of the reg. on that side.
As always, YMMV.
Jerry