I currently run 245/45/17's on 17"x9" Weds SA70's. I belive this is the group N (or N1) spec size of tyres for the R32 GT-R, I think I read this somewhere, or maybe I just made it up in me head............
I like the way the car handles on these, tramlines a wee bit but not too much, those 265's will be fun
The roads up here in NE Scotland are not the best surfaces to be running mega wide ultra low profile rubber on
I also prefer running 45's due to the fact of manging 2 rims with 40 (205/40/17) series tyre when running over raised steel cats eyes with my old 4x4 Sapphire Cosworth, never had problems with 45's. Just my opinion.
A 17" tyre, 255 or 265 will never be very close to the rolling radius of the origional 16" wheel and tyre combo regardless of the profile you choose, but obviously a 255/40/17 will be the smallest radius and have the least effect on the speedo/gearing. Do a search on the web, there are some rolling radius calculators out there. These will give you an exact measurement of various tyre width/profile combos.
Hope some of that helps you out.