Repairing heat exchanger

[Kiwibru]

My heat exchanger has major dents from objects hard and tall. Seems my heater air flow could be improved if I could remove the major dents from the heat exchanger. I don't want to spend $600 + for a new one so I had thought I could use a dent removal or puller tool. I would simply drill holes in the dents, pull them out, then slap on some weld to cover the holes.
Has anyone else delt with this issue? If so, how did you approach the issue?
TIA

[Profpinz]

I had a similar problem years ago when I restored my Pinny.
I cut the unit apart, around the weld line using a thin metal cutting disc and then spot-welded a thin stip of metal to one half only. I then screwed the other half to that.
While doing all this I took the opportunity to clean everything and remove the dents, then I had the cover sand blasted and powder coated, both inside and out to minimise rusting etc.
Now, every time I do any exhaust work I can take the unit apart and clean it out completely.
As regards the screws, I fitted "nutserts" and used stainless steel screws with anti-sieze, to make removal that much easier and simplier (it gets filled with dried, baked mud over the years), but you could just use self-tappers if your only planning on pulling it apart a couple of times.