I want to run enough to where I'm not going to burn mass, but I can easily switch to running those 6 miles. Anyone have a light to medium running program which keeps you in great cardio shape, but lets you get huge in the gym also...??

Disclaimer: I am basing this on my personal experince of being a heavy lifter (switching to running) I have been running for five months and have lost no mass. eat healthy and eat a lot, high protein, high carb diet. Lift at least an hour a day (I did 2 hours befor I got a full time job) you should see mass gained in a week or 2. one thing to remember make shure to rest between sets for muscle recovery. Thats my personal opinion please feel free to correct me.
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Forgot to mention I have a super slow metabolism so that may effect why it works.

Wizard--

If you're trying to become an operator you don't want to get huge in the gym. Why? Muscles require two things the operator and trainee doesn't always have a lot of--energy (food) and oxygen. If you don't want to become an operator then disregard.

Oh I do want to be an operator, but unfortunately I put into perspective when a reasonable time for me to go would be.....after school, after PRK, and a major change in training...this is in about 4 years (end of my reserve contract)...so I can get huge in the gym if im increasing running and swimming times and staying up on cals for now, and when the time comes to train hard for indoc, I can still stay big, but the switch won't be so dramatic. That is if I still want to go in 4 years.

yeah, like Tommyboy, I would say eat A LOT, that way you don't digest yer fast twitch muscles.

The easiest way to maintain muscle mass while running is to limit how much you run. Run three to four days a week and no longer than half an hour continously. Take a day of rest between each day you run. If you need to maintain speed, you can do speed work twice a week and 20 minute easy runs twice a week. Your speed days should be sprint/strides one day and short intervals on another.
For sprints, run 20, 40, 50, 60, 100 meter sprints. (Yes, I know the theory that the human body can only accellerate for 60m or less, but 100m fits better in sprints than intervals) The total distance should add up to 200m through 800m depending on how much speed you want to keep versus how much mass you are losing. Your intervals should be from 200 to 800 meters and should add up to 800-3200 meters, again depending on how much speed you want to deep versus how much mass you are losing.
If you are losing too much mass, stop the intervals or lower the distance of each interval and the total number of intervals. Another option is to drop one day of running. You can get by on three days a week easily enough. Option one is to run an easy day, a hard day and another easy day with a day off between each running day. Option two is to run hard, easy, hard, with a day off in between.
Give it a shot and see how it works for you.

Substitute some of your runs with jumping rope. I've noticed many of the mixed martial arts guys I train with are very, very big and yet they are in good cardio shape. Usually they'll run 2-3 times per week and jump rope 3 days per week for 20-40 minutes. Seems to work for them.

I just ran the NYC Marathon, it was my first marathon, and I lost considerable muscle mass, I lost density and strength in the upper body. But, I completed the run so I was happy to make the trade.