I would consider going with 4.88 gears. If you're going to buy a factory E-locker, going from 4.56 to 4.88 isn't going to change the price of a new diff.

You would have to replace the front gears, but one way to do it is with a 4.88 factory front diff out of a wrecking yard. Those diffs were found in some '92-'95 trucks that had V-6, 31" tires and an auto. Of course I'm assuming you have an '86-'95 IFS truck.

Usually they can be had for something like $150-300, then just bolt it right in.

You can run 4.88s with 31s, since Toyota used these gears in factory trucks. The only difference will be that 5 speeds have a slightly lower overdrive than autos and will run slightly higher rpms on the freeway.

If your running 33s, you'll be much happier both on and off road.