Well it's a Remington receiver which is fabricated from very strong alloy steels. I would want to examine it closely before making a call on safety. It's tough to see in the pic, but there needs to be some clearance between the safety lug behind the extractor and the front face of the rear receiver bridge. If the safety lug is bearing on the receiver bridge it will take up the recoil from the locking lugs at the front of the bolt which is an unsafe condition.
I've owned quite a few 03s, incl several Remingtons. I wouldn't have expected it, but I once found one with a cracked receiver ring. Assuming the headspace is OK, it would probably be safe to shoot. The drilling and tapping process, even though badly done, should not have rendered the receiver unsafe. The Remington 03s are known for their surface hardness and most often must be spot annealed before being drilled and tapped. The only way to absolutely determine safety would be to fire several rounds by "remote control" with the rifle secured in a rubber tire and a long cord on the trigger.
Quite apart from safety, the pi$$-poor attempt at drilling and tapping has ruined the appearance of this rifle. I wouldn't bother with it other than as a parts source. Quel dommage, as the French say.
