318 Engine stumble

Here is what I think I see from your photo's above:
- In the post #110 photo's, where the mark on the damper is at 0 on the timing cover marks (TDC), the reluctor points are lined up with the points on the pickup. This says to me that the physical alignment of the reluctor points is properly sync'd with the timing chain and pistons etc., so the reluctor is not the issue. This should be nominal 0* timing but the actual timing is retarded due to the pickup or it's wires not being right. It is firing at some other angle.....where the reluctor points are not aligned with the pickup's points. It is clear from later posts that the timing is quite retarded with this setting... which says the pickup is not right.
- In the post #111 photo's, it is clear that you have moved the body of the distributor CW, which retards timing even further. This is confirmed by the way the points on the reluctor are CCW relative to the points on the pickup. The timing is very retarded now. But we still do no know where, in the alignment of the reluctor and pickup points the ignition is actually firing.
- In the post #113 photo, showing where you think the pointing is for being around 0* timing, the distributor body has to be turned CCW to get the rotor to point here. This advances this timing and is logical to do so to correct the retarded timing from the pictures in post #110. BUT, the reluctor and pickup points cannot be aligned with this setting, based on the other pictures. So that says the pickup is the culprit.

Refer to the later photo in the last thread I linked, that shows the different wiring polarities for this pickup type. Next step ought to be to try a different polarity pickup.

AND be aware that this distributor, when configured to use with an external MSD ignition box, uses the reverse polarity to trigger the MSD module versus the polarity for the HEI module. So your distributor may very well have a pickup with polarity set up for an MSD box...which would be wrong for your HEI module. This is a cheap distributor from China.... so don't 100% count on it being correctly assembled out of the box.