Interchangeability - YZ450F Engines

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.

The '03-'05 YZ450's are functionally identical and will interchange seamlessly.

The swap of the 426 5 speed is not easy to accomplish, but can be done with patience, persistence, and a machine shop. The ratios in the '00-'02 5 speeds are quite similar to those in the '06+ models.

As I understand it, the bottom mount point and the swing arm pivot are in the same place on the new engines, but that's it. The cylinder on the new ones is near vertical, which could cause interference between the carb and frame.

Thanks. We're going to line up an '07 and I'll be curious to see how it looks. My '03 has the 426 five speed installed but I'm not sure it's something we'd want to replicate for a spare motor.

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