You ll need to find a corner such as in a closet to build a duct chase to get ducts from basement to attic.
Moving ductwork from basement to attic.
Drop sill would be hard to raise.
Even more important than that is proper location of the cold air return air ducts.
A drop ceiling could be fasten right below the duct work and that is about as much height as you could get.
I d definitely bring the heat ducts down to the floor.
You ll also need to provide a return path from a basement air handler or main level return to the second floor.
Is the duct work up aganist the floor joist.
All the duct work could be moved to one side of the basement possibly call someone and let him look at it.
That drop sill might make it impossible.
We went through and moved the ducts over to the edges of the basement since they tended to run right down the middle of the basement ceiling.
No thought was given in the basement to duct location.
Draw a floor plan of your home including the location of the hvac air handling unit the existing ducts sprouting from it and the room or rooms in your basement where you would like to place new.