by the look of it, they are set up to run towards the rear of the wheel, rather than in front as per the standard skyline caliper.
the larger piston should be in the dirrection the rotor rotates(rotor going clockwise, should be last piston past by the rotor).
so if mounted as currently set up, the piston will be on the wrong end.
you should be able to swap the bleed nipples, and transfer pipe(possibly have to get one made up), and youll be fine.
personally, if i had the cash, id snap these up, hot looking calipers, with pads and rotors...
just saving the dollars as we type.
good luck with sale, will be an awesome addition to someones car.