I dunno, I could make the argument the other way pretty easily if I were a judge. It would go something like this:
We want this race to be as safe as reasonably possible. Broken wheels/tires/brakes are very likely to cause immediate, unavoidable, and unanticipated extreme mayhem and/or unsafe conditions both for the car that is broken and for the cars around it on the track. Because we do not want you skimping on the very parts that most determine your safety (and, more importantly, your safety to others) on the track, pure safety items like wheels, tires, and brakes are free, even though we recognize that there may be a secondary performance benefit from fresh tires, wide wheels, and carbon-carbon brakes.
While an argument that 362-way adjustable Penske remote reservoir shocks (for example) are a safety modification because they aid in better car control thus leading to less mayhem on the track, they are primarily a performance modification with a secondary safety benefit. Similarly, although a 600 HP engine swap straight from Hendrick Motorsports may make you more safe by aiding you to avoid other cars and make your passes more swiftly, it is also primarily a performance modification. Performance modifications are not free.
Which category do wheel spacers fall into: one that if you fail to have them (like working brakes) makes you a danger to everyone else on the track, or one that if you fail to have them it might make you less fast on the track? If it's the latter, then I'd suggest that it's a performance modification and needs to be included in your budget. YMMV. Good luck.
Pat Mulry, TARP Racing #67
Mandatory disclaimer: all opinions expressed are mine alone & not those of 24HOL, its mgmt, sponsors, etc.