Originally Posted by Pre '68 Dave
In 1948 Chevrolet changed the process of the mains to allow "precision fit" bearings to be used. Before that the bearing inserts needed to be line bored once installed in the block.
So it would be safe to say that '47 and earlier had poured babbit, steel-backed insert bearings? If they were designed to be line bored, then there had to be a significant amount of babbit bearing material on them.

1952 5-window - return to "as built" condition | 1950 3100 with a 235 and a T-5 transmission