kbailey45,

If your engine doesn't fit the mount then either trim it up to fit your engine or get another one. If you decide to get a new one the holes may or may not fit the holes you have in the firewall now but it's no big deal to drill new holes. If you need to move the engine out so the spinner back plate will clear the cowl you may have to add to the fire wall. For example, if you need to move it out 1/4" then epoxy a piece of 1/4" ply or hard wood to the current firewall. As for the throttle linkage, that's always a tough one on any plane to figure out. You just need to get creative. That’s the fun of this hobby.