Your axle ratio is okay for the rig you have. The two most important things you need to consider if and when you encounter wheel slip on old seldom used ramps, are A: tires and B: limited slip in that order.
Premium wet weather, softer compound tires like Pirelli, Michelin or Bridgestones will probably be enough. If it isn't then consider getting a limited slip mounted in the rear differential. That will cerainly take care of it. I used to launch and retrieve 3K lbs of sailboat from the back end of a 3K lb Ford Faimont two door... but it had Pirelli P77s and they stuck like glue to wet ramps while wild and wooly looking pickups and SUVs with aggressive treads spun their wheels and got nowhere.

Simple getting all terrain tires is not enough, they must have a good soft wet weather compound with lots of sipes. Open agressive treads just mean less rubber on the ramp to give you traction.

If you have 17" wheels, then it looks like a choice between Bridgestone Dueler Revos and Michelin LTX M/S or Crossterrains.
You can see which one I bought below.

Oh, and one final tip... always have a full tank of gas when you are launching or retrieving... it puts more weight over the rear wheels.

Hope this helps.