I know its an old topic, but incase your still looking..
It would probably be easy to find some leaf sprung front D-44HD's with disc brakes from a 75-79 F-250. They can be had for cheap from $50-200 at a junkyard or local advertisements like the 'recycler' or penny saver'. They'll be stout enough for a small-lightweight truck like a ranger with 35-37 inch tires. Just upgrade the hubs and U-joints and you should have no problem. You could also try a coil-sprung D-44 from a 78-79 fullsize bronco. Full size widths only
A D-60 front axle, reccommended with kingpins(78-78 F350/ 86-91 F350) would run you 800-1200 bucks and are extremely hard to come by since they are very sought after by pretty much everyone and their grandmothers. however you wont find any of these smaller than full sizes widths.
For a rear axle, well thats up to you! There are tons of choices...if you go with the D-44HD or D60 up front....then you should go with a D-60 (not sure about what years had what splines) Or a D-70 or Corp. 14 bolt....for all out beef.
Either of which, you wont find anything this strong unless you have it custom built by Dynatrac or Currie as mentioned above and that'll cost you an arm and a leg. You could probably find a shop that will narrow those axles down for you, but the cost=benifit ratio wont be in your favor. Your best bet would be to buy a complete 70's era pickup or Rolling chassis with the axles you want, you could also swap use the perches from the donor as well.
With the strength of these full sized axles on a compact pickup, you'll find other weaknesses in your drivetrain pretty fast. I wonder if your master cylinder pumps out enough volume for the increased size of the brakes. Front driveshaft angle might be an issue at the end of the T-case. You could try 'doubling' your low range by using a "highboy" set up. Placing a divorced Transfercase behind your existing transfercase with a small intermediate shaft. You could have an insane combined low range of 6 or 8:1 and still have highway gears on your rig. This would be perfect for you since you say you like to go Rock Crawling in your rig. It would make for a bullet proof set up since its the gear driven NP205 thats driving your axles instead of the small chain driven ranger case.
Hmm you know what, my friend has a rolled 2wd longbed single cab ranger with a strong 4.0 and 5speed ......and I have an extra front D44, rear D60 and NP205.....Truggy time! hehe it just might be our next project though it wont have a second transfercase.