black smoke

94 Aerostar with 112000 miles pours out black smoke on hills and has no power will drop to 40-50 mph when climbing hills

First off the black smoke is an indication that the engine is running too rich on gas. If it's been this way for a while I think it would have caused the catalytic converter to be plugged robbing you of power when you need it. To tell, put a vacuum gauge on the intake right after you start it. If the gauge slowly goes down from 18 or so inches the cat is plugged or the muffler is plugged.