I have a parts book for the '03 thru '05 4Runner.
The rear bumper is the same P/N for all 3 models.
This is the center portion of the rear bumper:
1> 2005 Cover Bumper w/Trailer Hitch (P) - P/N: 52159-35100, lists $76.47 in the book.
(P) Paint to match.
Paint codes:
Black - 202
Blue - 8Q0
Champagne - 587
Gray - 1E9
Grayish Blue - 8R3
Red - 3QS
Silver - 1E9
White - 056
This is the end pieces:
2> Extension, Bumper Cover (P), SR5 Model - P/N: R 52152-35120 and L 52153-35120, lists for $174.12 each in the book.
There are 8 seperate parts altogether. The rest are small:
3> Retainer, Extension - P/N: R 52562-35010 and L 52563-35010, $38.44.
4> Bracket, Side Mounting - P/N: R/L 52185-60090, $9.17.
5> Retainer, Bumper - P/N: R 52587-35010 and L 52588-35010, $38.44.
6> Reinf Bar - P/N: R 52173-35050 and L 52174-35050, $7.46.
7> Absorber, Energy - P/N: 52615-35010, $46.30.
8> Reflector, Bumper - P/N: R 81580-60111 and L 81590-60141, $75.91.
Hope this helps. If you have any questions, you can post here or PM me.
Herb