06-07 forks are different. You can likely make them work in the 08-15 work by changing the length of them. Usually when I do that kind of work I am going the other way and making 08-15 Ohlins Carts work in the 06-07 forks which isn't much of an issue. I wouldn't know for sure if you can do it the other way around until I got them apart.
There was some good info in a thread here about swapping upside down forks into the '03 and '04 bikes. Among other things, it mentioned all the USD forks are the same outside dimension. In some year they got 10mm longer, and I can't recall if that was '08 maybe? Anyway, that thread may help you.