Look at the Autocenter web site....they give a curve for their
engines, even the stock GM Crate motors.

http://www.goautocenter.com/383_small_blk.htm

This page is for two 383 motors, one the stock GM job with iron heads and the other with the fast burn heads and a cam.
Other suppliers (except for the "fake crate" guys) will also give
some curve info......most probably present their best face so take it with some doubt. The point is that you can survey the reputable suppliers to see what they supply for components to get the HP that you want. Aint gonna do it with old style stuff without a lot of work. Look at Richard's dyno combos.....good idea of what is what. Five hundred is tough with a street driven small block.

mike in tucson