A man has been sentenced to 14 to 15 years in prison after pleading guilty to manslaughter in a 1976 slaying at a Gloucester funeral home. The Essex district attorney’s office said Norman Pike, 55, was sentenced Tuesday in Lawrence Superior Court. Pike pleaded guilty Monday just before he was to face trial on a first-degree murder charge in the fatal shooting of Eleanor Wadsworth during a robbery at the Pike Funeral Home. Prosecutors said Pike was one of three men who killed Wadsworth, the funeral home’s manager. Pike, the grandson of the business owner, was 19 years old. One suspect died before facing trial. Another pleaded guilty to breaking and entering.