The 1940 engine with Carter W-1 420s was rated 85 HP.

The 1946 engine with Carter W-1 574s was rated 90 HP.

The main venturi in the 574s is slightly larger than the one in the 420s.

I do not know if there were other engine changes 1940 to 1946.

With the air cleaner in place, the 420s and 574s look virtually identical

Carter W-1 carbs used by Chevrolet

If you are interested in how to tell the difference, look at the two different choke arms in the pictures.

Jon.

Good carburetion is fuelish hot air
The most expensive carburetor is the wrong one you attempt to modify.
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The Carburetor Shop