I wanted to get an evo 8 cluster and seats, to swap these in what modifications would need to be done?

 

https://www.evolutionm.net/forums/04...-04-ralli.html
https://www.evolutionm.net/forums/la...onversion.html
https://www.evolutionm.net/forums/04...ter-wires.html

All the above was found in under 5 minutes, and they answer your questions. We aren't trying to be a dick about it by telling you to search, but the mods are quick to tell you to search and will close the thread themselves...