If you want to race, go with an automatic. More consitant, easier on driveline stuff. So what if you lose 20 HP from it. The torque mulitplaction from the converter will more than make up for it. cheaper in the long run. My grandpa has a 383 nova that runs low 11's all day long and it is a four speed, he goes though a 600 clutch just about every year. Automaitics will last longer.
sure manuals are fun but, when it comes down to it, I would rather be at the end of the track than sittin there playin with my stick all day.