New Engine, Hard starting, Likes Lots of Advance

Hey dartman,............. think about that for a minute

And dart swinger,....... That cam will run anywhere from at least 6 or 8* advance to the same retarded. It just moves the torque peak around some.The cam timing is not the issue here.

65Dart
To my way of thinking,at this point, here are the most likely cause of your issues; 1)idle timing, 2)lifter preload, 3)vacuum leaks, and 4)carb issues,such as low speed circuit issues.
Forget about the cam timing.Forget about the balancer mark.You have thoroughly bugged those out.And by this time, I, at least, am confident that you know a thing or two about what you are doing. So, lets go to the less obvious stuff.
1)idle timing
"My ignition timing numbers are with both vacuum and centrifugal advance and running well above idle (maybe 2000 RPM)"
This is ambiguous at best.
Disconnect the vacuum advance,and plug the carb port.Set the power timing to 34ish degrees, at 3500rpm,or higher.Then report back.Leave the v-can disconnected for now.
2)lifter preload
Do you have adjustable rocker arms? If yes, are you sure the lash is set right? If no, do you feel the lifter preload was set right. Now dont go ripping the manifold off yet for a look-see.A simple compression test will tell you a bunch.
3)vacuum leaks
And finally, vacuum leaks. Im sure you know about the obvious places.But what about the not-so-obvious; Put a vacuum gauge on the crankcase(disable the PCV for a bit) and see if the intake is sucking air from the bottom.And speaking of the PCV, is it functioning properly. Or the brake booster. etc.
4)carb/.low speed circuit
I put this last, for a couple of reasons. Firstly I doubt this is the issue.Secondly,I believe the issue is among the first three. Thirdly, even with a non-functioning low speed circuit the engine could be made to sorta idle,well below 2000rpm.Now, a leaking PV, or a too high(flooding)float level, I could see. But the symptoms of those are almost overwhelming, and Im confident enough in your abilities that you would have recognized them.
Now, go check this stuff out.Starting with #1.Until the idle timing is set, no accurate diagnostics can be made.