The "925" is a full oil flow 261. The B58 means it was cast on Feb. 5, 1958.

Jim Carter has a good technical article on the 261.

Carter.


1948 3/4-Ton 5-Window Flatbed Chevrolet

34 Years. Now with a '61 261, 848 head, Rochester Monojet carb, SM420 4-speed, 4.10 rear, dual reservoir MC, Bendix up front, 235/85R16 tires, 12-volt w/alternator, electric wipers and a modern radio in the glove box.