Ours is the #3920 version. We're just hoping the float is ok on it. What I'm reading is that the 3920 uses the 7.5 gram float, which isn't even available used as far as i can tell.
The earlier cars took the lighter float, but the replacement later was the 12.5 gram. The 12.5 is the universal replacement. There is one for sale on eBay right now. Carter part 21-282 listed as Holley 1920 1bbl Carburetor Float.
To test your float, weigh it dry and then throw it in a container of fuel over night. Weigh it in the morning. If it weighs more, it is time to replace it.
