No rails are a straight swap.
You will have to buy some bride or other seats rails specific for the skyline as the stock rails wont work on after market seats, as i tried on my r33 which has the same floor plan under the seat area.
Check my sig for the group buy on r31-r33 rails, which has gone abit stale since i have to find a new company to make em and i havent got back positive numbers on how many want em