The 1980s were a golden period for male marathon running in the UK with higher numbers completing marathons in less than 2 hours and 15 minutes than before or since. Here is a quick summary of the training and other factors that they had in common:
In terms of volume pretty well everyone did 80-120 miles or even more per week.
Most runners ran frequent sustained long runs of 20 miles often at 6 minute miles or faster for 2.15 and faster male marathon runners.
A mid-week 15 miles was also common, again typically at 6 minute miles or faster.
Typically there were two faster sessions each week on track or road. Common sessions included 5-6 x I mile on the road and 12x400m usually on the track.
Despite most people working double run days were the norm. The commute to work and back was common, typically 6-8 miles each way.
Frequent shorter distance racing was the norm during most of the year but not was reduced during the marathon build-up. Usually no more than one half-marathon or 20 mile race in the 6 weeks before the marathon.
The typical build-up was 12-16 week with 2 to 4 marathons a year. Winter up to Christmas was mostly cross country training and racing. Many focused on the London Marathon every year.
Most runners tapered by reducing mileage by 75%-50% over the last 2 weeks and maintaining quality. The last long run was usually 2 weeks before the race.
Many top runners used a depletion/loading diet in the final week. Nutrition was more important than you might think. Many took some form of multi-vitamin with Vitamin C and iron supplements being common