The problem is, George, that it's impossible to tell! Years ago (too many) I was torquing the last head nut on a REAL 1750 Zagato Grand sport. The engine was warm and everything had been brought up carefully and slowly. It was very late in the evening at a friends body shop in Chicago. Much beer had been consumed. Suddenly, S N A P !
That last stud broke. There was a very very long silence, then the owner of the car said," There is nothing so silent, in my experience, as the silence that followed that stud breaking."
He was right. The next day I tore the whole engine apart again, and made a complete set of new studs. I would, however, do it the same way again as they did not look too bad.
I have seen really rotten, pitted ones on race engines hold up forever, while I have also had one really good one snap at a flaw in the steel.
If I was the owner of your lovely car, I would torque them to the correct 55 Ft./Lbs. warm, following Alfas text pattern in 2.5 Ft. Lb. increments. If one does snap, well, so be it.
It is NOT the end of the world, they can be replaced with new, using the top hat inserts as Stuart suggests. I have done the same. As I get older, patience seems easier to come by, and the rewards more important.
I would bet, they will hold up just fine, but, I have been wrong before. Have COURAGE!
Gordon Raymond
P.S. The old ones can be a real bear to get out. I usually send this project out to an EDM shop (a good one) and the job comes back perfect, and worth the price.