I have dropped floor pans. It's a simple fix, doesn't rub (the frame rails are much lower than the floor) and adds lots of room, even with stock seat rails.
But I'm only 6'-1".
I suggest you do what Dago did (that's his black racing Pantera GR4). Move the foot pedals forward and add this bubble on top. But Dago's only 6'-4".
So, drop the floor pans, keep the stock rails, get a more compressed seat pad foam and even your 6'-8" son will be comfortable, safe, sit correctly and enjoy racing a Pantera.
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