Curl:
Sorry, dunno. I have no experience with the 3 1/4 length brass. All my BELL brass was shortened from 3 inches, but my Bertram cases were ordered at 2 3/4 from memory. If not, they were shortened from 3 inches like the BELL. I certainly never gave neck thickness a single thought.

In a golden oldie like that AH, I doubt the neck area of the chamber will be at minimum dimensions. I don't think you'll have trouble. The only issue might be neck-cracks eventually in the thicker brass, but a neck-anneal every 4 or 5 reloads should take care of that. In fact, it probably wouldn't hurt to give the Bertram cases a mild neck-anneal after first firing, as they come necked-down slightly and tend to be expanded some by the initial seating.