Ok so I ran a 10k this weekend and had a good effort- 37:31. I know that sounds slow, but using an age graded calculator it's the equivlant of a 31:30. Much better.
According to the McMillan Running Calculator, I should be able to run a 2:56:04 marathon and a 5:12 mile. I've done the marathon time, but I need some work to run 5:12.