Corry,
Well it just appears to me that not very many people who build these engines preach some of the details that are preached in some of the other circles.
Counterweight cranks don't really allow you to idle at any lower speed (from what I understand...I've had an engine with a counterweight crank), what it does is kind of act like an additional harmonic balancer. By being counter weight it spins more easily, with less friction, and is another way to allow your red line to go up.....basically.
As far as learning about engine building and so on, I "grew up" learning about type 1 volkswagens...bugs.
Now the displacement in those are very small, and the redlines are relatively low for a small engine, actually very similar to many SBC's.
But building those engines was much more detail orientated.
For example, each cylinder was checked individually for the actually displacement. There are small variances between each. Light machine work is made to each piston to get all of the cylinders volume as close to identical as possible.
So I was just curious why nobody made counter weight cranks....
------------------
http://www.gruveb.com/z28 
If you are looking for a crank that is counterbalanced so that it can idle at ~200 RPM and "sound mean" I am not sure if these are available. These usually involve a higher, unbalanced rotating assembly and drop Torque/HP, so IMO it is undesirable.
