I just crawled under mine to take a close look and there's not much meat where the ball is (was in your case) attached; it looks like it would be pretty weak if you drilled it out big enough to insert a sturdy bolt.
There is an open space on the engine frame directly above that spot so you might have to weld a new tab there to capture the spring end. Anyway, a hose clamp and a "L" bracket would definitely be a temporary workaround; the frame leg of the "L" would have to point to the rear to work properly.
