Carb Studs or Carb Bolts?

I've used both and it's never made any difference ~~ except studs do make it easier to mount the carb straight the first time. As Pishta said, you're not putting any real torque on them so stretching really is not an issue. And yes, a washer and a lock washer on the carb flanges IMHO.
Edit ~ or a "ny-lock" nut as mentioned above.