Who would you let rebuild your Holley carb?

Since you don't have a ton of lift, the the 600 may be just fine; if it were a 650, I would say yes. And if no porting or headers, then I would be comfortable with the 600; the breathing restriction will be elsewhere. If it is small, it shouldn't do any damage; it will just run out of poop at higher RPM's a bit sooner.