Virtually any L-series oil pump will install on an L series engine. Also nearly all L series oil pumps have the same part number being 15010-21001. There are two exceptions. The first being 280zxt oil pump being 15010-S8000. This was the first and only change to an original equipment Lseries oil pump since the L series intro. The second exception is the Nissan Motorsports high pressure oil pump, 15010-A1110."
Now to the "why" in your question. "The output for standard and competetion pumps is 0.49 fluid ounces (14.5 ml) per pump revolution. The output of the 280zxt oil pump is 0.55 fluid ounces (16.4 ml) per pump revolution. The higher volume is for the additional oil to the turbo. It was accomplished with 5mm (0.20 in) longer gears, or 35mm (1.378 in.) versus 40mm (1.575 in) internally. Externally the turbo oil pumps are unchanged. High volume and high pressure are for the most demanding applications."
the above excerpt taken from "How to modify your Datsun/Nissam OHC engine" by frank honsowetz