The widest I would go is 275 on a 9x17in rim.
The only possible benni might be you can run lower tire press. if its a drag radial at the track as the rim will want to put itself into the rim more. 4x4 guys will sometimes do this to keep the tire seated at low psi...run say a 12.5 wide tire on a 8in (wide) rim instead of a 10in rim.