The real issue here is getting bigger reduces your ability to run distance for time because you're going to be trying to get oxygen to more muscle mass. At your present VO2 max with extra muscle mass, you'll get tired quicker because the oxygen you now take in will be spread across more tissue that demands its use.
On the flip side, the more you run to increase your oxygen intake and utilization, the more calories you burn, which makes it harder to gain the mass. It can be done, but it will require a caloric increase that takes into account the addition of mass as well as the increase of sustained activity(running). Keep in mind also that the increase in body weight will place more stress on the ankles and knees as you run.
In short, you need to sit back and evaluate your job requirements vs. your physical goals. You probably won't be Jay Cutler and run an elite 2 mile.