If the engine appears to be running well, I would not make any adjustments to the placement of the electronic ignition components inside the distributor. I would focus only on that external pinch clamp.
Per our earlier discussion, there are vertical and horizontal bolts for the dizzy clamp. The vertical bolts are shown in your first picture. The long horizontal bolt is not clearly shown but it will be obvious which it is. Loosen the horizontal pinch bolt and turn the distributor body to adjust the timing where you want it.
I also feel it is worth pointing out that you may be missing a distributor component. Your pictures show what appears to be a 25D6 series Lucas distributor. Look at the bottom, right of the distributor body in your second picture. You will see a "C" shaped opening. There is normally a thumb nut in that location. The thumb nut should be mounted on a threaded rod that is connected to the breaker plate. By turning that (missing) thumb nut you are able to advance or retard the timing by a few degrees as needed. The nut really needs to be there so the timing doesn't randomly change on you while driving. Of course... a previous owner may have locked the breaker plate to prevent that wandering timing... but that would also disable the vacuum advance.
I am not very familiar with the 25D6 distributor... only 4 cylinder 25D4. Can someone confirm whether the 25D6 should have the advance/retard thumb nut?