As I recall, I spent $50 to ship a front and rear 4.88 thirds across country last spring ('10) in 2 five gallon plastic buckets. So I think you are talking about $650 for a set of 5.62 gears, already assembled in a diff, ready to pop into your punkins. Alot of money? Yup! But.... these gear sets (5.38 and 5.62s) are about all that are available for increased axle gearing options for owners of trucks that came from the factory with 5.12 R&Ps. I don't think anyone is making these anymore either. The only other quick bump up grades would be transfer case gears.
Nothing like regaining the lost mechanical advantage caused by running taller tires. It puts a smile on your face that only a hard slap will remove. Suzuki thirds are built like the proverbial 'brick shithouse' and if the gear oil was changed regularly they should be good for over a quarter million (250K) miles plus.