I have a few questions I was hoping people could help with: Are the 2003 to 2005 YZ450 engines (I mean the whole engine and am really talking about hard mounting points) interchangeable? Would the hard mounting points of the 2006, 2007 and 2008 be roughly similar? I'm more thinking about ball park as this is a formula road race bike with a custom frame and there is some wiggle room, except maybe in the back of the engine case where the swingarm mounts. I think I am going to have this looked at first hand with an '07 motor, but I'm curious if anyone has insight or ideas. Our 2003 YZ450F motor is running a YZ426 5 speed transmission. Would the 2006, 2007 and 2008 5 speeds have quite different ratios? Thanks for any help. This is a new bike to me, and in the dirt I ride and maintain a Honda so I'm not too familiar with the YZ-Fs.