Professionally H/D Oil Pump. Fits L16. L18, L24. L26 and L28.
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 competition 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 is taken from "How to modify your Datsun/Nissan OHC engine" by frank honsowetz
High Capacity flow used in all our race and streetcars.
Same as High-Volume 280ZX Turbo Oil Pump, includes gasket!