There are three water pumps you will encounter from what I have found. One is the JDM spec 2jzgte water pump. This has some additional bits I believe to drive a little radiator fan that is offset from the main fan. It is advised to swap this for a USDM model.
In the USDM spec you will find the VVTI and non-VVTI pump. The VVTI pump has a smaller diameter for the center of the pulley and M6 size studs, non-VVTI has a a larger diameter for the center of the pulley and M8 size studs.
VVTI on top, Non VVTI on bottom
The pumps are composed of two main sections the front which contains the pulley and the impeller, and the back which contains the thermostat and bolts to the block. When replacing the front pump make sure you are buying for the correct pump body, the bolt holes will not line up for the most part.
When replacing the water pump there are 5 replacement pieces that should be replaced. The thermostat, two o-rings on the water pipe, one o-ring for the flange to the head, and one o-ring for the pump body to the engine block. Using hand soap for the o-rings is a nice trick to get them to slip in without ripping or smashing the o-rings on the thermostat and water pipe.
Image of thermostat, water pipe o-ring (second one is in the connecting neck not visible), and the connecting neck o-ring on the flange.
Edited by seattlejester, 02 May 2017 - 11:11 AM.