Like John said - in all seriousness you're probably better off getting a 20G from GT Pumps. They are good turbos and they're brand new and they perform well and they are cheaper and less mucking around than buying a dead 16G and getting it rebuilt and they are covered by a guarantee. You get the larger waste-gate flap, wider exhaust port and the comp housing is machined out to suit the 20G wheel.
Bite the bullet and spend the 'coin', you won't find many people will sell you a 16G cheap enough to make a rebuild to a 20G worthwhile and below budget.