I have been through this too and I agree that a lot depends on the floor from the seat back. It would be difficult to replace the floor as a whole. I took it on as a project to build and learn. I now have a truck that I enjoy. It is not perfect but I amd proud of how it turned out.

1951 GMC 1 Ton Flatbed -- It is finally on the road and what a great time I have driving it!
1951 1 Ton Completed

My Chevy Master 4 Door is on the Road!