I reckon a new water pump that stops your motor from cooking is the important thing. I would never even look at a water pump to see if it was NOS. But I do hate the look of the crappy after market fuel pump on my ute and also did not swap my inlet manifold for the new Edlebrock one I had because I wanted to keep the original manifold. Manifolds stand out like dogs balls to me. Try and find a good original one of them, but I think they would be very hard to find.
So.... if you find a nos pump for the right price grab it. Otherwise I would just be happy with good coolant flow from any new pump. But most importantly, run good coolant so you avoid buggered manifolds in the future.