Here you can certify anything. BUt if you modify a car too far, you end up rigistering it as a {insert year]LVVT scratchbuilt. All that means is you must run seatbelts that meet the current spec, Burst proof door latches, (Unlike dastun ones! lol) and a few other things.
The thing here which is gayer than aids that car peeps are raging about atm is new Camber laws. Due to dickheads with their pile of sh1t cars running MEGA neg camber then crashing, you can't pass cert with more than .5 degree Neg camber than the factory spec. I have a feeling that the rule will be amended in time. But people are up in arms about it.
However, much like hydraulic handbrakes, roll cages that extend past the back on the drivers seat, you can run them on the road legally if you get a motorsport Authority card. So it's not the end of the world.