Congratulations and welcome to Pantera ownership!
The Marvic wheels are a direct copy of originals down to being sand cast magnesium. The Roin are aluminum and I believe to original specs. You will spend roughly the same for Marvic as a 40 year old original set with unknown history and condition. The Campi wheels came in variants through the years many owners don't even realize they have mismatched wheels. You might want to consider purchasing a full set of 8's and 10's.
There's a great campi wheel article written by Mike Drew. I think available on the POCA site, you should consider joining, the access to documentation and old magazines, newsletters is worth the price alone.
'Clone's' are more what I would refer to as aftermarket aluminum wheels typically in 17" to provide a wider tire choice. If you really want this look then I'd bypass the 15" altogether.
PS. I think you will be bitterly disappointed in BFG's as a tire choice.
Julian