James,
The Tecnomagnesio wheels you refer to are extremely rare and have been out of production for a while. You can expect to pay upwards of $5K for a set (sans tires) IF you can find them for sale. All stock Pantera wheels were 15" dia., but there were various widths.
As Will suggests, the best option might be to order some 17" modern replica versions and coat them to look stock. You will benefit from better tire selection as well. Good luck.
Mark
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