1991 dolphin restore

My 1991 dolphin has extensive rot behind both front seat.. On the left side the overcab sleeper has dropped down and and was preventing drivers side door from opening. I have jacked it internally and got the side lifted and now the door will open. I will replace the floor first and then repair the wall question is how do I attach the two since the bottom trim prevents me from coming thru the outside wall to nail?

Any one have any knowledge of how it might be on 1991 dolphin

I suppose their are several different plumbing technics for this. I really want to find out for sure. In my 1991 Toyota dolphin