Talked to a gunsmith - its no big deal - you just need the stock, trigger plate and curved lever - they all interchange apparently.

EDIT - oh and the reason I would do it is because 1. I don't like the half-mag look 2. more weight = less recoil (although not a tremendous difference, 5 more rounds and that long barrel add some heft) 3. I like the look of that pistol grip - its pure asthetics on that count.