Wheels used in competition events?

[RIF RAF]

I'm in need of a new set of wheels and tire for road course (Time Attack) and auto-X competition purposes. Due to classing restrictions being primarily based on tire and aero I'm having a difficult time finding a set of wheels that will A) fit the car. B) safe at 100+ mph cornering speeds. C) not cost an arm and leg. Getting a competitive tire option requires sizing in a 275 or 285 wide and pretty much stuck at an 18" wheel. There's a few options in a 17 but fewer and not as good.
Those of you who drive the hell out of your car on a race track, what wheels do you use? Pros vs. Cons?

G body Cutlass
Wanting to move up to 18x10 wheels in a square setup. Not wanting to spend 6K on wheels and tires when I'm already looking at nearly that in safety upgrades.
Ideally for me there would be some 18x10 Nascar style steel wheels for a reasonable price out there.
I'll also throw out that I could run adapters to get into some more widely available bolt patterns and offset but I'm very unsure about the safety/reliability of it.
I competed in 5 auto-X and 6 road course events this year.