Trying to track down a slight surge and erratic idle watching the timing jump around, I found some great threads on timing bounce here. Yay Moparts!
After deciding on, then dropping the collar down past the cam, and somehow managing to get it back out, twice, I got it together.
Wow, what a difference that made.

Now that it's stable I can see that sometimes it starts to retard? (move to tdc) by itself until it dies or almost.
Then it might be good for a minute then do the same.
With or without the vacuum hooked up, mopar electronic ignition, 3x2. Runs great otherwise.
If it were fuel related would it retard itself 10 degrees while it's dying?
ECU wig out like this?
What to look for next?
Please.

Twist the rotor (rotate) & see how much slop you have in the intergear slot/dist lower tang relationship. dont twist hard enough to get into the spring tension just enough to check the play. 5 deg there (which ain't much) is 10 on the dampener

I checked for extra play at the rotor and it doesn't seem to be a huge amount. More like a wiggle than movement.
Timing stays in place until it starts retarding itself, will retard 6-8 degrees. Like moving the distributor, the timing moves before it starts to die, not the other way around.
New motor so all new bits related to timing pieces, turning the crank prompts almost instant response from the rotor, no real slop there.
Weird, I guess I'll just try throwing a few parts at it.
Could the springs in the dizzy be too weak to do their job?

Thanks for the suggestion, I'll give that a shot next weekend.
Playtime for this week is over.