As promised I took a look at an '03 WR450 left side cover today and compared it to my '04. The most obvious difference is that the idler gear cover on the '03 is flat and the '04 is raised a 1/4" or so. I didn't have time to make any critical measurements (all the other guys chomping to ride) but the actual engine covers look very similar if not the same. It looks like you might be able to install the 'torque limiter' by just changing the idler gear cover but I'm not sure. I hope this helps. I took some pics but I'm unfamiliar with how to post them here. Can anyone help with that?