A Monte cable would work but, all the parts houses only list a 3-Speed cable for the Monte for some dumb reason.
RockAuto shows both cables but, they have them listed backwards. They show the short cable for the 2004r?? Or maybe they have the lengths wrong??
1987 BUICK REGAL GRAND NATIONAL 3.8L 231cid V6 MFI Turbo (7) : Transmission-Automatic : Shift Cable Price Core Total
ATP Part # Y116 {Transhift Cable / 29.750 inches}
TH-200; w/Console & Range Select $15.42
ATP Part # Y651 {Transhift Cable / 26.15 inches}
TH-200-4R; w/Console & Range Select $38.79