1968 Chevrolet C60 Axle Nuts

[miller873]

Can anyone tell me where I might find new axle nuts for my 1968 C60 dump truck. Also, is there an axle nut socket that will fit inside the axle housing to remove the axle nuts. They are 3 1/2 inch. I bought a socket at NAPA and it won't go inside the axle housing. The locking nut was tack welded on the spindle and the outer threads are bad. Hoping to get the old nuts off and replace with new ones. I have a wheel cylinder that is blown is the reason for removing. I am also curious as to what the snap ring or retainer ring shown in the 2nd pic is. I haven't removed it yet. Thanks.