Agreed, it is cheaper to just pick up another axle with the right gears, and upgrade at the same time.
From 3:07 to 3:55 will put some pep in your step if you are keeping stock tires. A 3:55 MJ axle should be easy to find, but better yet, if you have the means to move the perches, there is an OVER abundance of 3:55 XJ axles out there in 4.0 automatics. Then you can get the 8.25.
My local JY sells them for $85. Regearing can cost $400 just to do it yourself, let alone if you have someone else do it.