There would be no pin to move if it isn't a 59-62 261 as there would be nothing to switch, since they were by-pass only (54-58).
the 54-58 261's are not full flow. It is possible that it has been modified to be full flow, or more likely as you say, he isn't fully understanding of what you're talking about. There are alot of people out there and on this site that will interchange "full flow" and "full pressure" without thinking...
If it's a full flow version, it's gonna have the 1/2" NPT holes for the oil filter lines, not the little 1/8" NPT ones like the by-pass versions.
Get the date code from above the starter and the stamped serial number (on the pad right behind the dizzy). That should tell you for sure what it is.
