Auction and private sales confirm that a well executed 'rodded' Pantera with tasteful upgrades can command as equally high and sometimes higher price. The Group 4 conversion in the photo looks to be a well executed example that IMO would appeal to a fairly wide audience as Group 4's are a favored modification.
Unless you are paying a premium for such a car I think it will hold value well and I believe future values for such cars may increase over originals as a new demographic ages and has funds to buy and enjoy one. Yes there will always be collectors of originality, but I look at those as more commodity investors. Look at antique car prices now, many are laughably cheap!