It all comes down to what you want the truck to do.

Taller than 38" tires, hi power engine swapped in and planning to climb walls. Then, the stock front axle is probably not stout enough to last. Especially if a front locker is installed.

Stock engine, hi powered ground pounder, 38" tall tires or smaller, no front locker and no hard core beating planned. The stock axles will probably last longer than the sheet metal.

The 5.87 gears in the stock axles are what lead most people to swap. Plus the closed knuckle, king pin, drum brakes and $200+ lock out hubs. By the time you change to a more street friendly ratio, put on lock out hubs and think about disc brakes. A set of CUCV D60/14b axles with all the goodies could be purchased with all the good stuff and money left over.

It all comes down to what you want to do. CUCV axles have tripled in price over the last 8 years or so. Now it is a dead even swap money wise.

I left mine stock, put on lock out hubs in front, a locker in the rear and my 396 Big Block has a NV4500 bolted behind it to turn the XZL tires. But, I am limited to 54 mph because of the NP200 tcase on long trips. The axles physically aren't the problem, just the gear ratio inside. A NP205 is my answer to the speed thing and the axles will be left alone.