Who is the largest NFL quarterback this year?

I feel safe answering that Colts 3rd String Jared Lorenzen is the heaviest ever, but that's not backed by any facts

Actually, you're right. Jared Lorenzen is 6'3", 275lbs. Second is likely JaMarcus Russell, 6'6", 260lbs. 4lbs shy of what he was when he first entered the NFL.