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What Tom said
Those planted bases are nice but they may add a little height and they look heavy. Brey Krause has floor mount adapters that add very little height, and they probably have a side mount with a seat belt receptacle mount which can save a few mm of height as well.
I would call BK directly and tell them what you want to do with the car, whether you are tall and need to maximize headroom, and they will tell you what you need. OG Racing can also tell you, and also sell it to you (unsure if bk sells direct)
Picking the seat is the easy part
the mounting adapters, brackets, sliders, sub bars, etc together can cost as much as your seat (depending on the seat) and there are many options.
I personally am running the BK 9044 floor mount with integrated sub bar, and no slider, for maximum headroom. The downside there is that the seat is not adjustable for other drivers and it is awkward to get at the access panel behind the seat.
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