Thanks all. It's 31mm stainless valves. I'm not sure what exhaust valves to go for . According to flow gurus it should be ok t stay on good 25mm valves or go for 26mm to be safe that also will support turbo if he power isn't satisfactory.
I know Erland, and yes he is great, and somewhat pricey. I normally Port my self and have seats put in by a competent machinist. I get good results. An additional benefit if Erland is he can flow test. Before and after numbers would be great for all on this forum an other gsxr oilcoolers. But it will add about 600£ to the total, but the head will also be better.