My personal favorite aftermarket wheels for the Pantera are Halibrand style.
I see Factory Five has 18" wheels that I think would look really nice. Based on George's guidance in Stick #8 it looks like they would fit. They may require 1/4" spacers as the offsets are more than what is recommended.
Front: 18x9 w/6" backspace (24mm Offset)
Rear: 18x11 w/6.46" backspace (12mm Offset)
Wheel Lug Pattern: Ford style 5 lug x 4.5" bolt circle
Factory Five recommends 255/35/18 front and 315/30/18 rear tires for their roadster application. I think 245/35/18 front and 285/40/18 might work better for the Pantera to get that 2" diameter difference George talks about.