performance valves for vn heads

after going roller cam in my 355 im abit worried about running standard holden valves?im after some info on what other people are useing.this is for my race only methonal 355?it has nearly 700 tho lift roller and should hit the line around 7500?this combo was shoewing around 550ish at the track ?what valves are around and what sort of priceing should i be looking at?Damo