Rusted trunk.

Looking for some feedback and suggestions.

My 73 Dart has a badly rusted trunk pan and extenstions, the obvious solution is to replace everything with new sheet metal but that comes with a premium price so I am thinking that another way to go would be to cut everything out and replace with square steel frame and individual panels. The main question would be, are there any known issues regarding gas tank support or other items that would require an original type trunk pan?
I have seen trunk floors like this before, usually incorperated with tubs of some kind, but wanted to get some opinions from members here before deciding which way to go.
I am not looking to maintain a factory restoration path so I'm not too worried about non standard fabrication.
The car will probably end up as my daughters learner car (she does not know this yet, he he) so getting a bit beat up will probably be in its future.
Thanks for any input..

Steve..