GM still makes the 14 bolt, so finding a new one with disc brakes is getting easyier. I dont know about this "E-locker" that you are speaking of, I know if its the Gov-loc then not its not a good locker for the reason I stated above.
Yes a lot of GM axles did come from the factory with the Detroit installed and yes the military CUCV all had 4.56's with the Detroit installed in the rear 14 bolt.
Thats what make finding a set of CUCV axles nice, a good deep gear to start with, a 60/14 bolt both SRW and a locker in the back.
But even if you cant find a set or want to pay the over priced cost that most sell them for ( the CUCV ), a simple 4.56's 14 bolt can be had for well under 200~150 at most junkyards.
Even if its got DRW hubs, the axle is the same width, but the offset in the hubs determine the WMS, so a cab and chassie axle is 63.5"s WMS, but with a simple hub swap you can make 67.5"s WMS.
Again nothing changes the axles shafts lenght them self, just the offset of the hubs.
The only thing that changes is the mount for the rear brakes is welded 2"s inward when it has DRW hubs, so when ordering a disc brake bracket from RuffStuff tell what axle you started with and he will ship the correct offset brake bracket for that axle.
Some trucks had the Detroit locker instlled and were used on the road, I had a few plow trucks with ( and still do ) Detroits in the back, makes pushing snow a lot easyier, even in two wheel drive.
I found my first 14 bolt with 4.10's and Detroit in the back, I had the time to go threw about 13-15, 14 bolt axles sitting in a pile of axles, I found a bunch of 4.56's axles but I needed 4.10s to match my front 60 at the time.
So I kept digging and found a locked, 4.10 SRW in decent shape and told the guy " that one ", paid 75.00 for it