Goob, the external oil line in your photo is not an identifier of a 261.
The only oil line/fitting characteristic that would ID/confirm a 58-63 261, would be 1/2" NPT oil line ports on the block.
Earlier 235/261 blocks would have similarly-looking by-pass oil filtration holes/lines. That line shown in your photo appears to be a small diameter line. It would also be a "cob-job fix" after removing the optional by-pass oil filter and lines.
