1971 Pontiac Firebird Speedometer Gear Usage

Information supplied by George Pearson
1971 Firebird Speedometer Gear usage Chart
  Driven Gear Or Sleeve Tire Size Speedometer Adapter    
Rear End Ratio Part # Teeth Color F60 X 15 F78 X 14 F70 X 14 E78 X 14 Model Ratio Part # Color Trans Code Drive Gear Teeth
3.42 3987922 22 GRAY X     X         WT-WO 8
3.42 3987921 21 RED   X X           WT-WO 8
3.73 3987917 17 PURPLE X X X X     6477964   WT-WO 8
Information supplied by George Pearson, taken from a Pontiac Parts Book