depends on which way you are built - long legs or long torso.
@HB Chris is much taller than either of us and
@Stevehose is too. i'm 6-3, but long torso ... so no issue on the leg room. many people put thick washers above the seat tracks to tilt the seat back more and increase the physical leg room. there is another issue with pushing the seat back further and that is reaching the steering wheel. i have a '74 steering column so it telescopes ... which is helpful.
i have no idea if longer rails are available or even possible. i have scheel seats so i use mounting plates ... the same is true with recaros and that can make moving the seat back a little easier.