I have a '73 Tour de France kitted with a triple and a 13-28 Dura-Ace 7-speed freewheel. The crankset is a Sugino PX.

The rear derailleur is a Simplex SX630 long cage. It barely handles the 28 tooth cog.

I suggest a front derailluer designed for a triple. I am using an 80s vintage Shimano Deore unit. I tried old Campy and Simplex fronts, but the shifting was slow and unreliable.

Recommendation: in terms of pure functionality, an inexpensive set of Shimano Deore derailleurs, matched with a modern Hyperglide chain and freewheel will outperform anything vintage, particularly the Campy drop-parallelogram rear derailluer.

That is, as long as you don't have a Simplex dropout/derailleur hanger on your frame. Then some mods would be required.