It's right under the crank hole bridge on the other side. Further complicated by a slight ridge going to the petcock drain.
Weld? Braze? JB Weld? Seal off with a bolt through and a thick rubber washer? Would you patch with a plate? Or drill a a hole through it to make it round and then affix a plug to it (braze/solder/weld around plug). Metal around the hole is fairly good. Looks to just be this spot.
Sorry there's no pic of the other side.
