1969 dart gt convertible floor pan install

How much of the floor do you need to replace? You could redo the floor patches if it is just front pans. But if the back floor comes in to play, then the full one-piece might be the better option.
I guess I am going with the RH and LH full pans. Was going to try it myself, but found a guy that restores old mopars and he said he has done both and finds the halves to be much easier. And he is going to butt weld them. Surely something I wouldn't try