[750hp]

Ant - stroke it, baby! You're killing two birds with the one stone when you buy a good SCAT aftermarket crank and rods. You get (obviously) strong parts, but the choice of how many cubes you want.
Anywhere from 3.7" to 4.0" is a good starting point. I personally wouldn't sacrifice rod length/stroke ratio for cubes by going over 4.0" stroke. For a nice, strong street motor, I'd probably be inclined to use a 4.0" stroke, 6.2" rods, nice light pistons +.030, and you have a very good base for a 408 cube torque monster.

I've heard some scary things about quality control issues with Eagle lately. I have some Eagle rods in a 460 in another car without a problem, but apparently things have gone downhill. I'd recommend the SCAT parts as the best value for money.