8:00/mile with a pack is pretty fast. Of course depends on length of run and size of pack.
Air Assault 12 mile "record" is around 1:37-1:38. Air Assault packing list runs about 45lbs. Fastest I've heard someone doing it is 1:37. Also, don't underestimate the effect of 12-16oz per boot, ACUS, flik, and carrying a weapon...:)
At Air Assault School in Fort Benning we had a guy on 1:37 pace through 7 miles then slowed. I finished right at 2 hours. Hardest part is running in boots, wearing a uniform in humid air, and carrying the weapon. If you did it in regular running attire plus pack it would easily be 1-2 minutes per mile faster average.
Alan