I would leave 1 inch of the old floor in all the way around the edge. Then lay new floor over top. Drill holes in new floor and plug weld onto the old lip.
I have a good book on this can post up on monday if you can wait
The closer you are to death the more alive you are
They are called drop downs as they don't attach to the inside of the rear quarters but drop down and connect to the bottom of the inner quarter. These are what I mean:
Installing the main part of the floor isn't an issue it's how to fix the bottom of the drop downs, they have holes in them as if they should be bolted in place.
sean, the bottom flange on the drop downs are suppost to overlap on the lower flange on the quarter ,theres no nuts n bolts used here. spot weld together. ive just finished installing boot floor and extensions on the satellite richard