Ok, here's what I got, and based on the assumption that some of these alternate class features are not the same feature and therefore stack. Two flaws.
Start off with a Feral Shadow Nezumi. That's LA 3 there, but starts with base speed 40, +10 from feral, and 150% from shadow. Ignoring the shadow multiplier for a moment, let's just look at the base speed, currently 50ft.
Fleet of Foot (the 1st level only version) makes it speed 60.
Quick trait makes it speed 70.
Two flaws go to Wild Talent for power points, and Speed of Thought. Speed is now 80.
1st level is barbarian, and we gain +10 speed. Speed is now 90.
2nd level is the wildshape ranger, which also gets an untyped speed bonus. Speed is now 100.
3rd level is druidic avenger, another untyped speed bonus. Speed is now 110. 3rd level feat is Travel Devotion.
4th level is cleric, with the Celerity and Animal domains. Celerity gives +10 speed, trade Animal out for Animal Devotion feet. Speed is now 120.
At 6th, or sooner if possible, pick up Run as we actually only need those four levels.
Get a ToB item to pick up Absolute Steel stance (Iron Heart 3) for +10 speed. Speed is now 130.
Get aforementioned Dark template item. Speed is now 140.
Let's review, right now with all permenant bonuses your speed is 140 ft x 1.5, or 210 base speed and 1050 on a full out run. We've beaten the requirements but lets go further.
Use the devotion feats. Animal gives a sacred bonus to speed by using the Cheetah option (it scales, +30 at 20th, so let's use that). Travel Devotion gives you an extra move action. Both activated as swifts and lasting for a minute. So speed is now 170x1.5=255 base speed, and with the extra move action running is x6 that speed, or 1530.
Then haste yourself for good measure in whatever means you like. Total base speed, 200x1.5=300 ft a round, or 1800ft on a run.
You get BAB 2, some alright hp, rage 2/day, and you can activate cleric magic items. With some Cha or nightstick abuse you can keep refreshing your devotion feets to have them when you need them. Switch Animal Devotion and Run, and the build comes online at ECL 7 (4 levels + LA 3).
Alternatively, be a spellcaster and polymorph into the biggest Mercury Dragon possible (I don't have the book on hand, so I can't say which one). They START at 200ft fly (perfect) and end up at 300ft. Most likely it'll cap just at the 250ft fly (good) age catagories. Apply any or all of the previous suggestions to said dragon and enjoy.