I'm getting closer by the day to firing the engine for the first time. Today I filled the transmission with ATF. As I was going about my business after filling it I noticed ATF all over the floor

After investigating the leak it turns out that the center of the transmission yoke has what looks to be a machined tapered hole. That's the source of the leak. Was this hole used for the centering of the yoke for machineing and then pluged with some kind of GM goo after?
My thought would be to use some ATV and a small screw and flat washer to plug it.
Anyone had this problem ? How did you fix it...
Jerry or John I know you have the fix.
Thanks Joe