The General Motors W-body cars received a supercharged 3800 V6 but only Pontiac got an update to this engine in '04. The Eaton Gen V M90 that came on this updated engine is more efficient and runs cooler which promotes better performance. But it is possible to use this newer technology in an older car.This is a walk through on how to perform the necessary modifications to swap a Gen V M90 in place of your existing Gen III.

General Motors engine codes:

L67: Series 2 3800 with Gen III Supercharger
L32: Series 3 3800 with Gen V Supercharger

Disclaimer: I am in no way responsible for personal injury or damage to your vehicle during this process. Whenever working in a shop environment safety practices should always be followed.

Tools Required:

10mm, 13mm, 15mm Sockets
5/16'', x2 15mm End Wrenches
5mm Allen Wrench
Serpentine Belt Tool
1/8'' Pipe Thread Tap
1/4'', 5/16'', "R", 7/16'' Drill Bits
Pliers
Small Hammer
Brass Punch
Flatblade Screwdriver
Torque Wrench
Dremel Tool with various bits for cutting metal
Ramps
Drain Pan

Hard Parts Needed:

Eaton Gen V M90
L32 Lower Intake Manifold (Optional but will make the job easier)
M8x1.25x120mm Bolt
M8x1.25x140mm Bolt
Gen V to L67 Throttle Body Adapter Plate (http://shop.zzperformance.com/store/p/114-Gen-5-to-L67-L36-Throttle-Body-Adapter-Plate.aspx)
x2 7/16'' Core Plugs
90° 1/8" NPT Male to 1/4" Hose Barb Fitting
L32 EVAP Purge Valve
12'' Section of 1/4'' Fuel Line
Coolant Elbows (Get the aluminum ones not the plastic)
Fuel Injector O-rings
Lower Intake Manifold Gasket (Also get the GM updated aluminum reinforced gasket)
Gen V Supercharger Gasket
Coolant
Oil & Filter

Step 1: Engine Tear Down

First you need to start off by tearing the engine down to the lifter valley.

The easiest way to start is to pull the car up on ramps to make access to the underside easier an then chock the rear tires

Now you are ready to tear down the engine

Disconnect Battery
Drain Coolant by using the petcock at the bottom of the radiator
Remove both serpentine belts
Remove dogbone mounts
Remove rear spark plug wires
Unhook fuel and EVAP lines
Unhook vacuum lines, EVAP line, and brake booster line
Unclip wiring harness from injectors, throttle body, EGR, EVAP, MAP sensor, and harness going to the front of the engine
Unbolt and remove fuel rail
Unbolt the alternator and remove
Unbolt and remove EGR heat shield and MAP bracket
Remove air cleaner tube from the throttle body
Unhook throttle cables
Unbolt and remove supercharger
Remove heater core hose from the alternator bracket
Remove Upper radiator hose from the thermostat housing
Unbolt and remove alternator bracket
Unbolt EGR tube from the LIM
Unbolt and remove the LIM

To see this in action watch the tear down part of this video.

Step 2: Lower Intake Manifold Modification Increase Opening Size

The opening on the Gen V blower is longer towards the shout side as seen in the image above.

About an inch of material needs to be removed from the snout side of the opening. To do this use a dremel tool to start cutting out the opening. The manifold is only made out of aluminum so the cutting should go fairly easy. There is also a small support beam under this section that will need to be cut before the piece will break free.

Step 3: Lower Intake Manifold Modification Plug Coolant Holes

Next You need the Plug off the coolant holes that help warm the throttle body. This is done because the throttle body adapter that will be used blocks off the passage in the throttle body and if not plugged can cause an air bubble in the cooling system. Plus this will help with performance since the air intake before the supercharger will be colder.

To do this

Drill out the two holes with a 7/16'' drill bit
Then using a brass punch and a small hammer drive the core plugs into the hole until they are flush with the surface.

With these two steps all the modifications to the LIM are complete. Now thoroughly clean the entire manifold especially the intake runners of any metal shavings.

Step 4: Gen V Supercharger Throttle Body Adapter Plate Install

The throttle body on the L32 in electronic controlled so you will have to use the L67 throttle body. As mentioned in the parts list you will need to obtain a throttle body adapter plate that can be purchased from ZZPerformance. This kit comes with all the necessary hardware and gaskets to perform this task.

Start out by removing the old throttle body from the Gen V (If necessary)
Now clean the mounting surface until there is no gasket material left
Use the provided RTV and create a bead around all the mounting holes a passage way (It is ok to use excess during this part just avoid getting the RTV in the screw holes)
Now using the four longer screws mount the adapter plate to the supercharger
Let stand for about 5 minutes
Clean off any excess RTV that squeezed out beyond the plate (Especially clean the inside of the inlet to ensure no debris will get caught in the engine)

Step 5: L67 Throttle Body Modification

The Gen V uses a different path for the air intake for the PCV system. So you will have to provide a path for this air. The source has to come from in front of the throttle plate but behind the MAF. This is a small section on the L67 throttle body but there is a brass plug that can be drilled and tapped.

Remove the L67 throttle body fron the Gen III blower
Turn the throttle body over and secure to a bench so it will not move while you are drilling (It helps to have a friend at this point because there are no good clamping points on the throttle body)
Locate the brass plug as indicated in the picture above and drill out starting with 1/4'' then move to 5/16'' this should just remove the plug
Drill your final hole with the "R" size drill bit this should be drilled all the way through the bottom of the throttle body
Use a 1/8'' pipe thread tap to put threads in the hole you just made
Screw in the 90° 1/8'' NPT to 1/4'' barbed fitting into the hole
Tighten the fitting so that the barbed section faces towards the front on the car when the throttle body is installed
Clean any metal shavings that remain in the throttle body
Install the throttle body on the Gen V supercharger

Step 6: Reassembly

Now it is time to reassemble your engine to do this perform the steps in step 1 in the reverse order.

Torque specs:

Lower Intake Manifold - 11 ft lbs
Supercharger - 17 ft lbs

When securing the supercharger, make sure the rotors still spin freely after torqued to specification.

Step 7: Final Modifications

After you have the engine assembled you need run a section of 1/4'' fuel line from the fitting under the throttle body to the nipple on the supercharger (seen in the left picture). The easiest routing of this line is over the top of the supercharger inlet as shown in the right picture.

In this swap you be switching from the L67 to the L32 EVAP system. To perform this swap just install the L32 EVAP purge valve into the supercharger (shown left picture) and connect the EVAP line. This may take a little patience as you need to carefully bend the line to the new location ensuring you do not kink the hose. Also since you are not using the stock EVAP you will need to plug the port on the throttle body with some sort of rubber cap.