Can't get timing dialed back to tdc

I am trying to adjust the timing on my 70 dart (slant six) it is showing it running about 6-7 degrees after top dead center at idle with advance line disconnected. I loosened the bolt on the distributor to turn in back to top dead center or a little before and it can't turn back any further,I can only advance it more. Could someone have installed the plug wires on the cap to far forward in the holes? if someone pulled the distributor before I bought the car to do the points is it possible they installed it slight off? I know it's usually dead on or completely opposite on most cars,but these have a gear instead of a slot that drives them.
I'm thinking maybe the fact it's running 6-7 degrees after top dead center (right side of tdc on scale with me facing engine) might have something to do with the fact it starts hard after sitting ten minutes or so after running,but fires at the bump of the key when it cools.

Any help surely would be appreciated.