It kinda matters what wheels you're using. The absolute largest OD rotor you can fit into a 15" Campagnolo of any width is 11.5". With 17" or larger wheels, there's room for larger OD rotors IF you modify the system with properly positioned calipers. Adding bigger rotors and leaving any calipers in the same place as stock gains nothing in terms of braking power.
And I agree- Porsches are a great source of parts. Back in the '80s I adapted a set of '70s Porsche (thin) vented rotors on all 4 Pantera corners, and used front 911-S (ATE) 2-piston aluminum calipers in back. I balance braking with a manual Kelsey-Hayes (Corvette) proportioning valve plumbed to the rear calipers. My separate, legal e-brake calipers are Wilwood mechanicals intended for go-karts.
One problem with ALL Euro calipers (Ferraris, Cobras & all Girlings including the Pantera) is, they used chrome-or nickel-plated mild steel pistons which will pinhole-rust in time. U.S. calipers (since the '60s) all use stainless steel. No pits, no liability. Check with a magnet- there are replacement caliper pistons of ss for everything nowadays. I made my own pistons of 316-ss for the ATE's back a few decades.