UPDATE:
OK...found out exactly what we were up against...they are not studs, but couplers. These couplers are beveled to accept a partial pen weld with a 3/8" fillet reinforcement. Got the sketch from the engineer this morning.
edit: Marty,
These are similar in design to what you are talking about.....They are beveled on one end for welding, and internally threaded to accept a large diameter rod/stud...and the ones that we have to use on this job are 1.25" and 1.63" outside diameter.