We own a house with an old oil furnace that works . The house was built in the 1960's by a contractor and has industrial blowers that are obsolete. They continuously break and parts are impossible to find. We had the AC unit replaced in 2010 and a contractor said he could replace the oil furnace with a heat pump and use the existing duct work for about $3500. Would we be better served to replace the furnace or the blowers? Is there even anything comparable to them?