See if you can get hold of Bruce Tulloch's training plans from '95 (in runners world) - they may be on this website (subscribers area only though I think). If you pick the 'Professional' set this should let you meet your potential. It basically has quite a few runs of about an hour; at least 2 hard sessions a week (intervals and/ or hills) and you will be running twice a day some days (one of the runs tends to be a 30 minutes easy recovery though). There is also quite a bit of 'steady running' which needs to be at marathon pace.
The intervals are this kind of thing:
1. warm up; 8*4min fast with 2min recovery, warm down
2. wu; 6*6fast with 2 min recover; wd
3. wu; 15min fast, 5min recovery; 10min fast, 5min recovery; 5min fast, 5min recovery; wd (this is a tough one if the fast really is fast!!)
I've always used these schedules and have worked well. It does get quite tough about weeks 8 to 11 as there is a lot of mileage and long tough sessions.