I can 100% verify that there was a difference in the 2003 model and the 2005+ skid plates. I too had to buy the newer ones for mine. EACH plate (Engine, Tranny, and Tcase) needs one hole drilled. The tranny plate shares a hole with the front, otherwise it will need two drilled. All other holes line up. I think that the 2003 and 2004's were the same, so you should see the same issues I had. It's a pretty minor deal to drill the holes. I am still using a stock 05 skid in the front, but upgraded to a Skid Row tranny skid.
Oh, and on the tranny skid, I think I just drilled the hole in the skid (in the back part) instead of the crossmember. This allowed me to use the factory attach point.
I do not know about the gas tank skid. It could be the same for all years. I use a Kilby tank skid.
Later
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2003 Liberty Sport 4X4
DIY Frankie Lift, BBS Rims, Aussie Locker Rear, DTT Front, Renegade Rack & Light Bar, Custom Front Bumper w/ Warn XD9000i, Custom Rear Bumper, JBA UCA's, Full Skids(Mopar, Kilby and Super skid), CRS Rock Rails, CB, EVIC, Nav, power dim mirror, (2) 8" subs under front seats.
http://www.cardomain.com/ride/2512777