Hi,
Your frame neck appears to be a -55 which just doesn't make sense with a L5 date code. Can you post a picture of the date code and possible the whole frame? I don't know if you want the input so my apologizes in advance for my comments about the frame. The front crash guard boss appears to be ground down and the "steering damper anchor hole" appears to be ground off the neck casting as well. I don't recall if you said you were trying to do a restoration or just a period looking rider? Something else that caught my eye and I am curious about, the top of the neck just under the cup papers to have had some welding and grinding done on it? If you provide the first two of your motor VIN we can probably tell you if your frame date code is reasonable. Again an L5 doesn't make sense because it would be for a 56K with the raised neck.
JerryR