No driveshaft loop required unless you have slicks(some tracks also require that for drag radials).
For a street car with street tires a helmet is all that is required. Also, most tracks will require a racing helmet(Snell 2000 or higher was already mentioned). Motorcycle helmets do no fit this requirement, but some tracks don't check. Both tracks I've been to(MIR, Capitol) have inspected my helmet.
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