I tried it, got so far and figured I lacked the skill and equipment.
Case at the far top (upper pic) is a side-shift OD. The center is a stock top loader. The bottom shows the opening enlarged .... with the white template the metal adapter that would have to be welded in.
I got this far. It can be done.
FlatheadODadapt2.jpg
FlatheadODadapt1.jpg