+1 on Old Britts, they will hook you up big time and are very helpful!!
As said before, watch that oil tank bottom. I shipped mine off to Matt at Colorado Norton Works, came back beautiful and no worries about it cracking and letting the engine grind to death!!
Read through the site and you will find a lot of help on everything.
Also, check out the International Norton Owners Association. They have some good helpful articles too, and a good number of meet ups!
Enjoy your new ride and the fun of keeping up an old snortin Norton! Oh, get yourself a set of Whitworth tools also!!