Wow, that's bad luck!
My best suggestion would be to have new ones made to fit your trunk. There's room for more volume compared to the original tanks, if made correct.
I believe the level sensors are equal to those on the Pantera, so new ones are available. You also need ventilation and tipover-valves. Mine are a Ford-product, but I don't know from what model. Sorry.
I will look in my files for pictures.
PANTERA INTERNATIONAL
A DE TOMASO CAR CLUB
Presents the De Tomaso Forums
The On-Line Meeting Place for De Tomaso Owners and Enthusiasts From Around the World
Clicking on the banner will take you to the sponsor's website.