FWIW, I have made a Ching Sling setup for a few Marlin 336's for friends with a 1" carrying strap attached at the front of the mag tube with a QD swivel/clamp, and at the sling's rear with a wood forend-type swivel QD stud with maching threadfs/nut ILO wood screw threads.
I trashed the machine nut, shortened the threaded part of the QD stud, and installed it in the bottom/front of the 336 receiver's bottom metal, replacing the screw there.
With a 3rd QD stud in the buttstock's normal position, the rear of the sling can then either be hooked up under the receiver in the Ching position or as normally at the rear.
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