You are right about not wantng to pay for a new gear swap if you are only going to go to 4.56's. However if you are going to pay someone to install the lockers, $200 more per diff really isn't that much, and most of the work is already done just to install the locker. Also if you pull the 3rd members and IFS center section and take it to a shop you can save several $100's in labor.

You can usually find used IFS front diffs for under $150, I paid $250 for a used one w/5.29's and a tru-trac for my '91 flatbed. The rear w/new ARB and 5.29's was only $1150 through Davez off road, not sure what the shipping would be, but they do ship. You can find them through the Pirate 4x4 venders site.

What is the mileage on the engine, have you adjusted the valves, what is the compression numbers? If the comp numbers aren't in the high 160's it might be pointless to add a cam and head w/oversized valves w/o rebuilding the engine.