I'm guessing you won't get much in the way of marathon-training advice here...so I'll give you what I can. From 2008-2013, I was a sorta-competitive-ish distance runner (took it up to lose weight after playing college football, before the pendulum swung me back towards a strength-based fitness approach). I ran a bunch of half-marathons (four or five sub 1:30's, personal best of 1:27) and one very painful full marathon, and along the way got to train with some pretty good folks. I like lifting more now, but the running community can be pretty cool and major marathons are a really interesting event, so kudos to you for taking on the challenge.
So first...I think an important thing to figure out for yourselves is how much you care about doing well in the marathon vs. sacrificing other elements of your training and fitness. Realistically, if you're giving an honest go at a strength training program like 5/3/1, there's no way you'll be giving "marathon training" a full go...and that's not necessarily a bad thing. If you're in it just to get to the finish line upright and in one piece (i.e. running to "complete" rather than "compete") you can get by on a bit less running and probably maintain some of your lifting routine.
You're still way out from the race, so I would gradually scale back from four 5/3/1 workouts per week to three per week and eventually two per week (maybe for the next month do four per week, then switch to three per week, then switch to two per week by the time you're 16 weeks out). Each time you remove a 5/3/1 workout, add a short easy run (maybe 2 miles) in its place. Once you are comfortably running 2-5 miles three or four times per week, you'll probably want to start upping the mileage. Do this gradually, and keep at least a couple of those as truly short-and-easy run days (i.e. don't just pile more miles on all four days uniformly; go from running 2-5 miles three or four times a week to something like two 4-mile days, an 8-mile day, and a "long" run which I'll explain in a moment).
You can find many different beginner marathon programs around the web that will have different permutations and combinations of mileage, but all have a couple common threads: a gradual increase in total mileage, a long run that accounts for anywhere from 20-50 percent of the total weekly mileage, a periodic cutback week, and speed work in some form or another. Speed work is entirely optional if you're just in it to finish the thing. The real key for a low-mileage marathon runner (relatively speaking, anything under 30 miles a week is low mileage for marathon training) is getting at least a couple of truly long (16-20 mile) efforts in to get yourself somewhat accustomed to spending that much time on your feet. Not every week - but ideally you should probably get at least three or four of those guys in before the race.
So a typical week now might look something like this:
2 miles / 4 miles / 2 miles / 4 miles
About 16 weeks out, you should be able to do something like this:
4 miles / 6 miles / 4 miles / 8 miles
About 8-10 weeks out, your training should start to look like this:
4 miles / 8 miles / 4 miles / 16 miles
4 miles / 8 miles / 4 miles / 12 miles
4 miles / 8 miles / 4 miles / 18 miles
4 miles / 8 miles / 4 miles / 12 miles
4 miles / 8 miles / 4 miles / 20 miles
About 2-3 weeks out, you should start cutting back and probably cap your longest run around 12 miles. By that point, you really aren't going to get significantly fitter, so the focus should be on getting to the starting line healthy, rested, and ready to roll. Many a beginner marathoner has screwed themselves up by running a 20-miler one week before the race.
Other miscellaneous tips
figure out what you can drink during a run. Many a beginner marathoner has screwed themselves up by just drinking water during training, then drinking Gatorade because that's what the race was giving out...and given themselves all kinds of lovely GI issues. I was lucky enough that this never got me during a race, but you really don't want to have to stop for 4 minutes at a port a john and then have to start running again.
figure out what you can "eat" during a run. Similar to the above...many a beginner marathoner has screwed themselves up by trying one of the fancy GU energy packets that the race was giving out when they'd never tried one before, and ended up with sickly sweet stuff stuck in their mouth because they didn't drink any water with it. For what it's worth, I don't think GU and its cousins are necessary - if someone is on course to give you a banana or some peanut butter or honey that may work - just be advised that you'll want to experiment with this a little bit.
figure out what you can eat the night before a long run, too. I would not advise getting the all you can eat clams and scallops the night before a race if you usually eat steak and vegetables. Also, the night before a race, bland is probably good, and a spicy burrito is probably bad.
Ummm...that's about all for now. Oh, and start doing a yoga class once a week if you can find one, preferably the day before or after your long run. That might be handy, too.