If the goal is to "keep it original" as much as possible, you should re-lace that Campy Gran Sport hub (after re-packing it) to the closest rim you can find to visually match the Weinmann. Trouble is, nobody makes a modern rim with a similar "bead" down the middle, and that's really OK since you can find a modern rim that's better in every way to the Weinmann. If you really want a match you'll have to use galvanized spokes, too, but here again I'd opt for "modern" stainless and never look back.
Eventually you can rebuild the front to match the rear and be good for another few decades.

BTW, I looked at the pics and you already have some anomalies on that bike (the tires, the saddle certainly and even the Pivo stem and Sugino crank may be same vintage but might not be OEM, and the Mafac Comps might be upgrades) and you eventually WILL be replacing the Simplex RD (oh yes) and the FDs already been done...so don't be too hung up on "purity"...Gitane certainly wasn't when they built these bikes!