Here are the parts I used for my Hitch detail (Class IV 6500lb). Take in mind that my 2004 GX did not have the tow package and needed everything from the relays to the wire harness. Oh, and I wanted this hitch as if it was from the factory.
1. PT22860540 Towing - Hitch Kit – Class IV
2. 8216960050 Towing – Wiring Harness – 7 PIN
3. 8198560020 Relay Box (green)
4. 9098702016 Fuse Box Relay (requires 2)
5. 08925-35870 Center support bracket
6. 52169-60052-B2 Bumper cover (give your color code)
7. unk part # You will need new bumper reinforcement braces.
The factory ones that come on the vehicles w/out
tow package come together at the center where
the Center Support Bracket goes. I am going to
cut mine to work (cut off wheel). You will also
notice that the wiring harness comes with a
mounting bracket and so does the Hitch kit.
Use the mount that comes with the Hitch kit
along with a small cut to the driver side rear
bumper Reinforcement brace (see pics).
That should do it for the total install. I know there are correct bumper reinforcement braces but the cut off wheel made short work of the required changes. As for the bumper cover, I have three of them (see pics) and they are all a tad different color so don't expect it to match exactly.
Hitch on showing the cut braces.
cut out for the wire harness
both braces cut and painted, ready to put back in.
Now make sure you have the correct center support as there are two. The hitch (PT22860540) I ordered called for the 08925-35870 center support. Here are the two different ones side by side. I originally got the wrong one. I do not know the part number of the first one I got but I understand it is for the 20003 and early 04 GXs and the hitch part number PT228-60440.
As you can see the new one on the right shows the mounting holes located more to the rear of the vehicle.
The new one is now on the left showing the part number.
The new center support in now on, ready to put the bumper braces back on. Notice there are two thin spacers that were used in between the center support and the hitch.