Randomly, I had to do something very similar for measurements (weight and volume, ie pounds, ounces, grams, gallons, quarts, cups, etc.). I was saving mine into a MySQL database, and outputting to everything.

Basically how I ended up doing it was storing it to the metric measurements (grams/liters). That way you don't have to figure out (in your case) "8 miles, 6 yards, 2 feet, 9.75 inches-- it's just... well, I have no idea what that is in metric, but assume a number like "47533.008m", and from that all you have to do is a stack of mods and divs, and you should be able to pull out your values properly (in either units...)

Doubt this'll help, but it got me out of a couple minutes of work! =)
Mark