Cast crank engines are used often in drag racing. While not as strong, the cast crank is lighter. Make sure you order rods for the cast crank.
The cast crank rods are narrower than the the forged crank rods. (This can also benefit a racing engine, as there is less bearing surface, so less friction.) Prepare the rod bearings appropriately for use.
If you haven't already, hit the Home button and read the Articles. You will also find a lot of great information by perusing the FAQ in the Engine section. Look up Doc's builds, and look over the Engine Build Matrix.
Enjoy!
CJ