Early A 727 Speedometer hole

Alright, I keep changing things on my rear end and I am tired of my speedometer needing constantly needing adjustment. I am going with a GPS Speedo, but now I have a hole in the trans for the cable. These early A's have a different speedocable, the y-804z, and I need find a way to plug the hole in the trans. Of course, they make plugs all day for mustangs, but I am finding nothing for us Mopars. Anyone delt with this problem before? The male transmission end of my cable is .9725in across and seals with an oring and single bolt.

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