What I did to check piston position is place a wooden stick (not from a tree) into the cylinder and marked how far it came up and marked that position on the wheel. Then I turned the engine over just a little bit. Checked with the stick, marked it, marked the wheel. I did this until it advanced up to the top of the cylinder and then back down. That allowed me to know whereabouts TDC was and it certainly matches the timing mark.
That is interesting. My vacuum is connected to the port on the very left of this image (not the choke in the back, the port with no hose on it in this picture):
http://www.carbkitsource.com/carbs/images/carbsnapshots/carterBBD-68Dodge-large.jpg
It definitely is creating vacuum at idle, which is maybe a problem? Let me know if this is the wrong port.
I know vac advance works decently enough because there is a significant effect on the engine when I connect it via the hose mentioned above (from 250rpm to 800rpm).
Any more thoughts?