Interesting.
Over the last few years I have noticed alot of professional team sports players (football, league, rugby, auusie rulz etc) have begun to develop alot more muscle mass while maintaining their aerobic fitness.
At a gym I used to attend a friend there who was shooting for a spot in a professional team used to combine a weight programme (essentially what I was doing) with a full fitness regime. While I was 'hard out' doing my bodybuilding he would have done the set of the bodybuilding exercise and thrown in some 60 yard sprints or something in between. It was amazing to me that you could develop so much fitness and retain a good deal of muscular mass also.
If you can run marathons and put muscle on - good luck it will be a hard road to travel but if you can do it I'm impressed.
Just thinking - if you look at the tri atheletes of today some of those guys and girls are very well muscled while having peak aerobic conditioning so it can definately be done. I guess sprinters are very impressive but their overall fitness and aerobic capacity most likely wouldn't match that of the long distance runner.