For the rear end, it may be a 4.88. Mine was a 5.13. Topped out at about 48 mph! I put it on jack stands in the rear and turned the drive shaft until the tires went around 1 turn. Count how many turns on the shaft and if it is under 5, probably a 4.88. You can get a 4.11 if you'd like to go a bit faster on the highway!
