For any kind of sanctioned racing (and as good practice) the bulkhead bar should be modified to have 4 anchor points as the two at the extremities are not sufficient to prevent flex in the bar under a hard impact.
Best for a full cage is to find a shop local to you who can build one in the car, thus keeping it tight to the outermost points. that said, all the vendors sell bolt in versions, the three point are least intrusive to cabin space (third brace extends top the appsenger footwell)and some come with that piece removable for every day driving if you carry a passenger a lot.
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