It is interesting that in the three parts books I have that cover P11, the 1967 P11 spares list calls for P/N 23877, the '67-'68 parts book that covers both P11 and Atlas calls for P/N 23877 for both P11 and Atlas. The big book that covers '66-'67-'68 Twins shows P/N 034048 for '66-'67 Atlas and '67 P11 and P/N 034070 for '68 Atlas and '68 P11A.
What I take from this is that Atlas and P11 shared the same side stand leg. Furthermore, that leg was changed for the '68 model year and the P/N for the early leg was changed to 034048.
As for the longer leg from Joe at Eurotrash Jambalya, I have found that his reproduction parts are not always exact. I know the length of this leg was questioned some time back and the person was told that it may be a little longer but it held the bike straighter.
Also the rear fender support he sells is listed as P11 but is obviously a P11A ranger item. When asked if he had any for the early P11 the reply was "They are all the same."
I'm not commenting on the quality of any of these parts, but I suggest you know what you are buying.