You will need conversion fenders, the R34 fenders wont bolt straight up.
http://vivagarage.com.au/Products%20Page/N...ders_TypeC.html
Not sure about how reliable VIVA is, but it should give you an idea. Although you can merge R33 and an R34 fenders to get something a lot stronger, altho it will be more work.
Good luck, if I was keeping my R33, this is the conversion I wanted to do.