R33 GTR pump in a gtst is good.
Can't say much about it seeing as mine was fitted by a mechanic, but i had the stock pump, a bosch 040 and now the gtr pump in my r33 gtst. I'd say it has the power capacity similar to the 040, but it's probably more reliable.
It also sounds good, whirring away, compared to the other two pumps. If you stick your head under the car it sounds really noisy though, it's a big buzzing sound.
But try get the whole assembly if you can, beats stuffing around trying to fit it.
If you don't have a better option i'd recommend this mod.