I'm going to guess 1973, based on the serial # and '73 - later "Raleigh" graphics. I've seen Gran Sports with either Stronglight 93 or Nervar Star cranksets but not with a Campy crankset as factory issue. Original hubs would have been Normandy with 27 11/4 alloy rims. Rear derailleur looks like a Campagnolo but it is at a wonky angle, as though someone may have mounted it to the hanger for the Gran Sport's original Simplex. Seatpost and front derailleur also upgraded to Campy. Certainly nothing to complain about here component-wise. Being as the original handlebar tape has been replaced, and the replacement tape is pretty beat up, I'd guess the bike did do some mileage before the owner's mishap.
Being as the bike came with 1 1/4 (32mm) wide tires and the frame can probably accept 27 x 1 3/8 without clearance problems, converting to 650B may not be worth the expense involved. If the geometry of this Gran Sport is similar to mine, it will make an excellent "all-surface" bike.