9 weeks to marathon or 14 weeks for sub 1:30 half

running eye

I have been running fairly regular now for just over 12 months covering 1300 miles last year. My half marathon PB is 1:36 last July. I got injured in September and reduced my mileage and speed for the end of the year. I have ran 180 miles this month with a lot off road fell running and just ran my first 13.1 miles since September in 1:50 (fell running) and a 43 minute 10k (road). I am 42 male and 136 pounds. I have two goals which I'm battling with, a sub 1:30 half Sheffield in May was my original aim but very tempted to enter Blackpool marathon which is in 9 weeks if so would aim for 3:30. Which is more achievable? I feel I could run 26.2 miles at 8:00 mile pace but upto now 15 miles is my longest run. I would be joining a 16 week plan at week 7 but don't look to have missed to much as a fairly high mileage in January anyway. Or would I be best to up the speed work give my self a bit longer and try to break 1:30 for the half. Any advice on which one to do best way to train for it would be greatly appreciated