I have a 69 with some what of the same problem. It's the adjustment on the column linkage, If the floor shifter
is not pushed all the way forward I have to turn the sleeve on the column to get the car to start. With the linkage
being so old on these cars you start to get wear on it. I could only adjust so much. I have to rebuild the linkage
between the column and the transmission, that's on the things to do list.