I've been using the Clevite H-Series Tri-Armor coated bearing for my small-journal 327. Competition Products had a number of different sizes available. I know that King also has the small-journal bearings in their most recent catalog, and they make a quality product.
No guess on the old shells, I'm afraid. A lot of companies made engine bearings back when that motor was new, but it would make an interesting search! Could you take a picture of the number/stamp?
Good luck with your 283 project! What's in going in?
Lew