Replacing the whole floor in a vert is very time consuming and is much more work than a Coupe because of all the added support braces. I am doing a 69 vert right now. If you don't need to replace the whole floor, I wouldn't.
From the pics, it looks like you need new firewall and torque boxes. The torque box welds to the firewall and extends up to the upper frame mounting locations. There is also a brace that welds to that corner that looks like it's missing or completely rotted thru.
