this is a 1991, but it's very easy to spot the ONLY difference.
see the nipple with the hose attached over by the dipstick? Aside from the fact that on a 1990 that nipple doesn't exist, 1990's are identical to 1991's.
1990 waterpipe & water neck are each missing a single nipple that goes to the garbage water/oil mixer... err cooler. They still have the fittings to watercool a turbo. The difference between a 1990 & an NT pipe & neck is that the NT stuff doesn't have the provision for watercooling a turbo either.