Hi, I found myself in the same situation. I bought a "complete" S/C kit pulled off of a 2003 Tundra 4.7l. The kit came with every wiring harness, TRD piggyback unit, hardline fuel pipe and banjo fitting but was missing the water inlet housing. Original owner had already scrapped the Tundra and did not realize that the water inlet housing was unique. I ended up having to buy a second "complete" kit just to get the water inlet housing.
It is possible that you can have one made up by a good fabrication shop that works with aluminum, but you'll have to go through the install of the S/C just short of the water inlet housing and let them have the truck to make up the unit and fit it properly. Beware of "experts" out there that tell you that you can go with shortened bolts on the existing water inlet housing, you will see once you go through 3/4's of the install that there is no way there will be adequate clearance for the body of the housing and the S/C belt.
If you have a spare vehicle, a good fabrication shop willing to take on the task and the time, I can tell you that there is a market out there to start selling these water inlet housings (I'll be your 1st customer). This is the one piece that is currently IMPOSSIBLE to get, so you can start cleaning up by buying incomplete kits on Ebay and the boards, add in the water inlet housing and charge $4000 all day long for the complete proper kit.
Do not be turned off by the stories of the TRD supercharger blowing up motors, it is simply a matter of not overboosting and keeping temperature ranges down. Here are the rules to live by:
Stick with the stock pulley sizes
Get temperature range 7 spark plugs (Iridium BRKEIX7)
Get the lowest temperature thermostat you can (161 degree ideal, 170 degree will work fine with regular coolant servicing)
During the install, take the time to clean your fuel injectors and do a basic rebuild on them (replace upper and lower o-rings, filter baskets, etc. Kit costs less than $50, insurance is priceless
Spend the money to get the UniChip ECU instead of the TRD piggyback ECU, the tuning is MUCH better than the TRD unit and can be customized for additional add-ons
Do not be afraid of CAI's, headers, etc, just make sure you tell the boys at UniChip what you're running so they can set the map properly
If you have the option, there are 2 versions of the 4.7l S/C, a 9 injector unit and a 10 injector unit. The additional injectors are used to intercool the compressed air charge, so go with a 10 injector unit if you can
To be safe, start running full synthetic oil, switch to a 3500 mile oil change schedule and get yearly transmission services if you run it hard, doing the regular tranny fluid flushes will help greatly since the Gen1 tranny's do have metal alloy weaknesses that can develop
As for me? I've got a 2000 Tundra Limited extended cab with a 10 injector TRD S/C, 170 degree thermostat, K&N CAI, throttle body spacer, Iridium BRKEIX7 plugs, rebuilt fuel injectors, JBA ceramic coated headers running to a Magnaflow cat back dual exhaust, all managed by UniChip. When I blew my original rear end I replaced it with a 2004 limited slip unit. Truck is completely debadged and discreet until you hear the turbine spool up and scream through the Magnaflow exhaust
