My suggestion would be:
10:1-10.5:1 505, TF heads, small street roller cam.

If I were building it for my own use, since I like doing my own heads......I'd use Indy EZ's.

Actually...... If I were going to build it right now...... I'd use what I have on hand......
Which is a low deck 511 rotating assy with flat tops, and some 84cc E Street heads.

You can easily get to the pump gas 600-650hp mark with a bb stroker many different ways.