Regulae's advice doesn't look bad however, you mentioned 'full marathon training'. Does this mean you ARE running the marathon?
If so, as you well know, a marathon is 26.2 miles not 18. You need to have long runs over 20 miles in distance ...if you can get your base mileage well over 70, then your long runs should be over 20 too. Some would suggest over-distance ie; 28 - 30 miles...a few of those anyway.
>>pure LSD<<
Some people use this method to stave off chronic injury, which is advisable for someone in this position however, if you are injury free and not injury prone then LSD in it's proper definition may be too slow if you want to run a marathon well.
...or just change what the acronym means, to Long Steady Distance...'slow' running, unless you are recovering from a hard workout is only going to help you run slow.
Run as many miles as you can fit into your life, at the best possible pace, for as long as possible.
So that means if you are too busy, then fair enough, but as many miles as possible is the aim during the base period. The best possible pace does not mean sprinting or racing, but the top of your aerobic limit as much as possible. So yes some days may be a little slower than others. For as long as possible means as many years or months as possible.
When you plan your key marathon race, count back 12 weeks and transition into faster running, starting with more hill work....more on that some other time.
Watch your quality during the base phase. If you go super fast and get super out of breath (anaerobic) you spoil the aerobic condition you are trying to build.
So faster running as speed work is ok, but don't go so hard that you need to stop and recover....