Below is the part of the STS rules concerning brakes, I have bolded the relevant sections:

A. Non-standard brake rotors may be used provided they are of equal or
larger dimensions (diameter and thickness) and made of ferrous mate- rial (e.g., iron). Thickness includes the individual plates of a vented rotor,
as well as the overall dimension. The diameter for replacement rotors is
measured at the minimum outside dimension. Aluminum rotor hats are
allowed. Cars originally equipped with solid (non-vented) rotors may utilize
vented rotors. Cross-drilled and/or slotted brake rotors may be fitted
provided all such voids are within the disc area and comprise no more
than 10% of that area. Brake calipers and mounting brackets may be re- placed provided they bolt to the standard locations and the number of pistons
is equal to or greater than standard. A functioning emergency brake
of the same type, operation, and actuation as OE must be present. Drum
brakes may be replaced with disc brakes of a diameter equal to or greater
than the inside diameter of the standard drum. Such conversions must
be bolted, not welded, to the axle/trailing arm/upright and must include
an integral, redundant emergency brake. Changes to backing plates/dust
shields/brake lines to accommodate these changes are permitted but may
serve no other purpose.

B. Brake lines may be substituted with alternate DOT-approved flexible
brake lines.