Haha - Nice thread hijack samuri
UWISSH - I don't know if you will find many R33 GTR owners who run your exact size and offset wheels with 285/35R19's as well... But I'll see if I can help.
If you have 275/30R19's on at the moment and they are running fine without fouling on guards or suspension I would recommend sticking with them if possible.
However, if you want to up-size to 285/35R19 you'll need to do some measuring first because there is a significant overall diameter and width difference between the 2 sizes... Also, remember that different brands will have different widths even though they have the same size printed on the sidewall, tyre sizes are only comparable within each brand, not brand to brand... I have seen differences of up to an inch in width between tyres listed as the same size in different brands.
Here's some info on these sizes:
275/30R19 - Approx O.D = 647mm (depending on tread depth), approx width = 260 - 275mm (depending on the brand).
285/35R19 - Approx O.D = 682mm (depending on tread depth), approx width = 270 - 285mm (depending on the brand).
Thats a difference of approximately 35mm in diameter and there could be a difference of between 10mm and 25mm in width (you won't know until you physically measure the new tyres).
My advice is to get under the car while it's sitting on the wheels and suspension (not on a jack) if you can maybe use a 4 post hoist so that you can measure the room you currently have between your tyres, suspension and inner guards... If you don't have enough room in height and/or width then it's probably not a good idea to upsize.
I hope this helps