How do you know that part came from that hole?
It seems it would have to be more substantial than that to hold oil pressure. I would think something like a "freeze plug" but what do I know about tractor engine design?
Russel King is 100% correct, that part did not come from that hole. I was hesitant at the dealership when told it was the proper part but buddy wasn't interested in helping me confirm it was the correct part. I paid my $1.11 and left.
I ended up tapping the hole and installing a pipe thread plug.
It was a hairy procedure as the tap broke off in the hole, yikes!
My wife helped me bleed the fuel lines and we both crossed our fingers for start up, it's alive!
I've since removed the rad and am going to inquire about having it recored. Hoping to be back in business by Friday latest.
Thanks again to all who have offered advise.