Problem getting tumbler aligned to remove

[Sygma6]

Howdy folks,

I have a tumbler that is kaput for my 84 300SD and am having some trouble getting everything aligned to push in the pin so I can unscrew the lock barrel sleeve. On the front the indestructible metal cover is spinning freely of the rest of the tumbler so I do not know when I have everything aligned right




So, I am thinking since the green plastic on the rear does move with the tumbler if we assume that the pin on the left for the vacuum connection is 12 O'clock where should the middle of the rounded plastic bit (red dot) be so that everything is aligned to insert a pin to unscrew the lock barrel sleeve?



Thanks a lot for your advice.