Technical U-bolt plates on '56 Ford - what are they made of?

Okay, I realize this is probably a good way to prove my ignorance, but the spring pack lower plates on my '56 Ford Fairlane need the shock hole welded up and re-drilled. I can't believe they would be made of cast iron, since they are put under a load so often, but I want to make sure before I ruin them for good. Any help will be greatly appreciated.

 

If they look like cast, they're probably cast steel which you can weld easily.

 

I wouldn't think that they would be cast iron. Try the spark test with you grinder, a good spray of sparks from your plate should be good steel, cast iron will not have many sparks. Bob

 

They are cast iron. I hit a spot on the edge with my wire-feed and it just melted. I guess I'll make some.

 

If it is cast iron that little bead you did with the wire feed will be hard when you hit it with a file...

 

I've never heard of cast iron U-bolt plates. Can't for the life of me imagine why anyone would make them as a casting