"From 340 to 3:40 in 2007"

this is an idea i'm kicking around:

going from 340lbs to a 3:40 marathon in 2007.

it's very ambitious.. Because I know for a fact that I can run a sub-4:30 marathon - even a sub-4:00 seems likely with smart consistent training.. But I'd really have to work hard to get a 3:40 marathon.

I admit I'm harboring a dream of qualifying for boston - in which I'd have to run a 3:10 marathon. Something between a 7:25 and 7:30 min/mile pace for 26.2 miles. I'd like to turn that dream into reality. Last year, I proved that I could do a marathon. This year, I'm going to prove that I can do a marathon well.

The first stage is weight loss with base training.. losing over 100lbs (already lost 40), and building a base of 20 miles per week and starting to do speedwork. the second stage is, of course, marathon training - adding long runs into my schedule..

any thoughts?