Of course it is possible. Make one run a tempo run on the weds, then make the sunday run a long one. Gradually build them both up. If he has a good base, then he will be fine. I did a sub 3.30 marathon recently on only 2 runs a week. Good luck.
I personally think that 50+ miles, and running over 5 days is really not necessary if you want to run sub 3.30. I can understand higher mileage for a sub 3 hr, and it is probably necessary for the over 40's.