DS2 - the Runner's World sub 3 schedule has delivered me two sub 3 marathons - including this year at the age of 56. Mileage peaks in the low 60s and I include one track session in that. I know nothing about HADD, P&D and I don't do the different pace sessions that the Runner's World one recommends, but just try to keep my overall pace for the week up to below 07:30, 07:15 on a really good week. As I live on the edge of the Cotswolds there is a lot of ascent and descent in that.
Ohh yes. I also do the full 26.2 in a training runs but absolutely nobody recommends doing that!
As an oldie, you get my vote, but of course as an oldie I don't how to vote and shock horror I am not on any social networking sites!
The Runner's World magazine for January has a big article on marathon training which you might find interesting. One of the case studies is on someone even older than yourself I guess.
Good luck!