My copy of the "Chevrolet Pickup Red Book" (Motorbooks International, 1946-1972) says for 1949:
Total = 383,543
1/2T = 201,537
3/4T = 97,668
1949 is the only AD year that has that breakdown. This out-of-print book is really hit or miss.
There are more complete production numbers for post-AD trucks (C-10, C-20, K-10, etc.).
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.