Acceptable 'eyebrow heights' -- That sounds bizarre, an administrative rule that requires a lookup table.
Are pre-70 vehicles exempt? Any rule about covering the tread width? Are fender skirts (front and/or back) disallowed? Re-arching the fender?
suspension travel -- dropped spindles OK?
Cutting/heating/lowering blocks -- This sounds commononsensical. What does you tire sidewall measure [at]?
While I like the shiny metal grille block/airdam on Bombshell Betty, there is a thread on an
Aerodynamic Bumper that has currently dropped to the bottom of page 2 in this forum. He takes cooling air from in front of the wheelwells and it seems to be a good strategy.