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.
I have bought a lot of old Edelbrock manifolds. (LD4B and D4B's) If everybody used studs the carb and thermostat threads wouldn't be all stripped out. I recommend studs for any aluminum fastening unless it has steel inserts.
