Hi
Hot rods right about sticthin'but if your lucky you can also use Devcon Titanium filled putty
If you rough the surface up and get it really clean this stuff works wonders
I gets hard enough to drill and tap
I have used it on some very old stuff that I didn't wanna mess with and thought the crack/casting wouldn't welding or stichin'
Once you have smoothed it ion you can texture it with an wet terry towel or shop rag to look like the iron around it.
Might be a really good idea to make a small batch to play with on something else first.
Got first place once at a concours with this car in Unrestored Class at Torrey Pines
It took me days to unrestore that old car!!