Rear floor supports

[cackshifter]

I am just replacing a rear crossmember on my 90 CSW and just before welding it up thought I might as well put some paint on the rear of the floor etc and the top of the crossmember while I could still get at it. So...I ran the wire brush (on mini grinder) across the bottom of the last few inches of floor to remove a decade of crud, and lo, the rearmost transverse floor support developed a hole - or 3 to be precise in front bottom and back faces.

It looks as if it has been pop riveted to the logitudinal supports above, but they seem to have forgotten that and the whole lot is loose, except for the ends, which are riveted in somehow to the edge of the wheelarch, with 2 somethings, looking like an aircraft rivet and rather sturdier at each end. Anybody got any idea what those fasteners are, is it possible to remove them non destructively or does Mr Grinder need to be involved? I though at first I might patch it in situ then thought I might as well take that support out and either do it on the bench or replace it, now I'm beginning to think I might as well take the floor out and do it all properly, as I'm sure it has flaky friends further forward.

One thing I can say is if you put an airline on the ends of those floor supports and the little top hat sections in the wheel arches, an unbelievable amount of muck flies out, even though it has been jet washed. I'd recommend it but you'll need a shower after (or get someone else to do it).

So, if I decide on the radical approach can you get the centre rear floor in and out of the rear door? Is it just a matter of stripping the centre out, replacing the supports and replacing the floor sheet or is it more complex?

Nigel