[OrrieG]

The attached pic will help you id the type. To determine if it is posi jack up both wheels and turn the passenger side, if drivers turns the same way it is posi if it turns opposite way it is open. Make a mark on the pinion shaft and have a helper turn the passenger tire one full radius while you count the number of times the pinon turns. That will give you an idea of the ratio. If you want more accuracy, turn the wheel 4 full turn, count total number of pinion turns and divide by 4. Common ratios are 2.78, 3.08, 3.54, 3.73, 3.90, 4.11 and 4.56 which would correspond to the number of pinion turns.