Chevrolet W-1's up through the 483s came with the solid pump link. The 574s (post WWII) came from the factory with the spring as shown. Also, the solid link on the 483s (1941, 1942) was to be replaced with the spring during service.
The 684s (1949 only), due to the funky accelerator pump, used a totally different solid link from the earlier W-1's.
The 1949 carburetor had MAJOR engineering changes (lots of parts are very different, and may interchange, but not successfully, with earlier years). As Chevrolet downgraded their carburetor (opinion, others may differ) in 1950 to the Rochester B; parts for the 1949 carb are much less common than for other years. All parts, including kits, are available; but much more expensive than for the earlier years. The repair kit for the 1949 which contains the correct accelerator pump is unique to the 1949.
Jon.
