Ok, So I made just a tiny (really tiny) bit of progress today. It was more of an exploratory job on my "new" cab than anything else. As I suspected it seems like someone attempted to cover up a rust hole in the cab corner, by wrapping a patch panel over it. Only thing is, they did not finish the job.
So, I cut out the patch panel they installed to see what was behind it. As I figured it was another rusty piece of metal. Based on what I found back there, and the overall condition of the drivers side floor edge, I think I am going to replace the drivers side floor with patch panel (see pic), and the rear cab support. The drivers side floor edge is not in the best of shape which is why I am thinking of replacing the whole thing rather than just the rear part of it.
Any thoughts on if this is the right move? Is there something else I should be working on other than the floor panel and the cab support?