Hi,
I know this may not be much help, but i started driving that same route from sixty eight till eighty five, obviously a long time after you, but even then a lot of places had been bypassed, with dual carriageways and the A1m, what i'm trying to say is, if you could find the dates of the A1 diversions you could maybe take a look around the areas where it no longer runs,
now, maybe you could solve something for me, i remember many years ago, on the A1 way past Doncaster, there was a long downhill stretch to a small roundabout, and you took the third exit if you were going north, in effect it was a right angle turn, but I cant for the life of me remember the name of the place, and no one will believe me, maybe you can remember,
cheers, pete.