Unless you are running tires with different heights front and rear, it sounds like you were sent two different ratio's, and one end needs to be regeared again. You need to find out what gears are in both ends so you know which gears to order.
If you don't want to pop the covers and count teeth, you can lift a corner, mark the driveshaft and the tire, spin the tire two rotations (or one rotation if you lift both tires, I think?), and count driveshaft revolutions.
You are fine to drive it in 2wd until you get the correct gears installed, just do NOT use 4wd. You may want to just pull the front driveshaft to be safe.