I've managed 323.1 mph (Escudo) on the top speed test w/out the wheelie. Although I did bend the rules a bit.
Set ASM & TCS to Zero. Lowest possible downforce (F&R), Set gears at widest, then push all gears (individually) to their farthest setting. Except 6th, set it at 1.073. Final drive gear at 2.000. I think I set the VCD at 23 front 77 rear (Adjust required).
Super soft tires, maximum modifications. Break in the engine to increase the HP to 1881. This is done by running a slew of qualification laps at the test course. Keep checking your settings w/out exiting for each increase. You'll likely need an oil change at some point The break in should happen around 200 miles.
When you've reached max HP go into the Test course. (here I bend the rules a bit) At the Start, throw it in reverse, and back up just around the previous corner. Hold the E-Brake, and Hit full throttle. Release the Brake, and you should start to hurtle forward. Do this a few times to track optimum shifting points. NOT when you hit the rev limiter, but when your acceleration starts to slow. You will FLY down the straight-away, and hit the wall on the curve. You'll bounce and pick up a few more MPH/KPH. Well over the 300MPH mark.
Keep in mind that your tires will be smoking until near the end of 5th gear.
Now that I have a Sharkport, I should be able to load a replay to the web.
AO