For the rear it will be fine. 265/35/R18
Front 255/35/R18. (35 being a % profile) therefore it will have a smaller tyre wall than the rears
or 255's all round.
It is the offset that matters most, and I wouldn't go larger than +30 GTS_T
I think Kasko's going +22 so will poke out.
Camber, ride hight will come into play.
If it's going to be dumped somewhat then gaurd rolling/pumping may be needed.
Best advice would be Mick out at National Tyre Wharehouse (NTW) Fyshwick