I have a block with the casting code of 3835911 and a distributor pad stamped number that shows up as that for a 1954 Corvette. However, the block is definitely a 261, as it has the steam holes and a 3-3/4" bore. I was told by the previous owner that the short block was purchased as a replacement engine in the mid-seventies to be installed in a '54 Corvette. I remember seeing on the Inliners' site a few years ago of another 3835911 block that turned out to be a 261. It was also believed to be a replacement block.
The casting numbers and the distributor pad numbers are just evidence, not proof, of what the block really is. I own or have owned five 261s, and ony one of them has both numbers being correct for a 261.
Hoyt
