Nothing under the present floor boards so your good to go there, as for a step by step procedure I'm not really sure that anything like that is out there; if you like contact Kirk Evans @ 1-419-874-0505 he is a Pantera restorer and did the floor pans on my group 4 Pantera.
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.