Start with Boyce Equipment (Boyce Equipment Axles and Military Parts) to get some ideas.. they have complete conversion kits (but you can do it more cheaply, usually, by putting a kit together yourself) then go on Pirate Off Road forum and see the axles available at reasonable prices in the forums classified or by dealer (1000dollarman).

You would be looking at a Rockwell conversion (military)
roughly a 6k pound front axle.. rear to match.. ratios as previously stated above..
These axles are plentiful all over.. ebay etc... and there are numerous aftermarket parts for them.. from mild to wild.. from lockers hubs to disc brakes to shaved pinions

You can also get a military transfer case.. manual or air shift ..usually Rockwell as well.. or even use a bulletproof 205 if you get the right drop

I have done a number of rockwell conversions and they are straightforward (on 70s vintage f600s).. steering for you will be the most difficult aspect to deal with (I dont know what your steering box looks like on that year).. but again it is a fixable issue

have fun

notme