73 rear brake cable

so the new in the box doherty cable which came with the bike is longer and the pin dia is also 8mm vs ~6mm for the original cable part # on box says ZZ9925A and "made in England" and there was no pin with it

since this was bought about 18 yrs ago by the PO i have no record where it came from.

do i drill out the foot pedal to take the new cable or is this just the wrong cable?

The new one looks nothing at all like the cable on my 73 850. Mine is exactly like your old one. Don't drill out the pedal just buy the correct cable. On the Old Britts website it's part number 060482. I just replaced mine last week and it fit perfect. $33 USD

"ZZ9925A"
https://www.feked.com/rear-brake-cable-norton-commando-750-850cc-models-1968-74.html

LAB ; was this cable an upgrade and is the pin and lock clip also upgraded? as they were not included.

I don't know.
It's possible the Doherty ZZ9925A cable wasn't made correctly. Motoparts claimed that his stock also looks like the "new" one in the box..