Studied a little more on the floor last night. I think I'll try this...
I already removed the seat (raised) pan (suburban). The floor is solid from the front of the pan back. It is a good flat straight line all the way across there for a cut. Before cutting I'll do a bunch of measuring! Then go up the toe pan 3" or 4" to get to solid metal, again cut. Braces under the floor look soild (if not I'll buy replacements). Take this cut out piece and make a 2-piece pattern to show the local metal guy and see what he says $$$. I'll have him roll some beads for strength. So I'll end up with 2 pieces and make cutouts to match the old ones, Tranny, batt, master....
If the price is reasonable I think I will give it a try, still a lot of winter left here
Buddy