Well, based on where they are, I think two of the dents could be pushed out from behind by going down the tube from the flange. You would need to make or buy a curved spoon or dolly to get down there. The third dent is going to be the tough one to reach. You'll probably still need some heat to help with the hammer and spoon/dolly work if you go that route.

I think the curvature and the metal thickness are both wrong to be able to use something like a bullseye pick, which is unfortunate. I still think a (stud welder type) dent puller might work well, but it's going to take some decent force to pull a dent of that depth at a bend on a piece of tubing. Probably need some heat and a slide puller.

Might as well try freezing water. It's a dented header, what's the worst that can happen?

I just came across a suggestion for drilling a small hole on the opposite side of the tube, then using a punch through the hole to push the dent out. That's pretty brilliant, if it works...

 

Thanks for the suggestions Farik8!

That's the way I'm thinking though, it's already dented what's the worst that will happen? The bottom one is not nearly as deep as the others and is the only one that's got a slight crease. I figure if I can get the two other ones I'll be pretty happy.

 

The funniest thing I came across was a suggestion to find someone who repairs brass horns (the musical kind). I can't think of someone with more specific skills for exactly what you need, assuming you can find someone like that. Might be worth a shot, unless you're trying to stick with the DIY approach.

 

Haha, I didn't even think about that at all!

I had spoken with a general purpose stainless manufacturing place, they didn't want to mess with it because they couldn't guarantee their repair would be what I want.