Nitto offers a 335x30x18 NT555RII drag radial on their site, click here =>
Nitto NT555RII 335x30x18 that they list with a 44 psi max operating pressure. The tire has relatively stiff side walls and at the pressures they suggest, I suspect, very stiff side walls — not your typical drag radial. They are also DOT compliant, which is a nice touch.