Hey, since no-one else has entered a valid entry, here goes:
Human Ex-Barbarian 1, Monk, level 18.
Abilities: Natural Con 18,
23 after stat increases.
28 with inherent bonuses (wish, tomes)
34 with +6 enhancement bracers
Equipment: Monks Belt, Boots of Speed
Feats: Run, Dash, Great Fortitude, Endurance. any 4 others.
Spd 105 ft.
Race 1:
For the sprints, 105 feet in 6 seconds.
Running: 525 feet in 6 seconds.
Endurance Race 4:
I can run for 34 rounds before making a save. My save bonus is +28, and rolling a 2 on a d20 gives a result of 30. Therefore, I can run until (at least) 20 additional rounds, easily beating the 50 round time limit.
Running gives a speed of 525 fpr (feet per round), times 50 rounds gives 26250 feet total.
subtracting two standard actions to activate the Monk's belt and Boots of Speed, that's 25200 feet. However, this allows 20 partial actions. The partial actions I will partial run in (PH p. 127) for 1050 each, or 21000 for all twenty. total of 46200.
46200 feet in 5 minutes. Average speed of 924 fpr. 8.75 miles.
[edit] added Barbarian level [/edit]