Go with 335/35/17 tires in the rear, they will fit with the right offset wheels. As for wheels, spend the little extra and get the wheels you like...you won't regret it, unless it interferes with the wife buying shoes or something. Or if that is the case, ask around and get some nice used ones from other Pantera owners which will have the correct offset. Some are selling 17" now and going to 18", so you may find some nice ones out there.
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.