Not sure of the compatibility of the two carbs. Just curious, what is the purpose? Is something wrong with yours? I was thinking that the 06-08 carbs were the same, and the 04-05 are the same. Same goes for the exhaust systems. Looking at the microfische from Service Honda, all of the carbs utilize the same TPS from 04-08, part #16060-KRN-671. The only talk I ever heard on switching carbs was to run a 05 carb on the 06 bikes due to tuning issues with the increased size of the 06 (if I remember correctly they went from 37mm in 04-05 to 40mm on the 06-08 bikes). I think now this has been remedied on the newer bikes. If you are having issues with your current carb, it could just be jetting. I would try to repair/retune what you have before dropping $400 over what could possibly be a $5 jetting issue or possibly a jet kit fix.