Radiator issue

I have an original radiator from a 69, and I can run my finger down the cooling fins, (the thin metal folded down the radiator in between the coolant lines) without damaging them. I would even have to use some force to get them to bend over - not that I want to.
I also have a radiator for a 67 that has been rebuilt, and on this one if I even touch the cooling fins they will collapse. The metal is thin.

The 67 radiator is the correct date coded radiator for my car.

What's going on here? Is it just that the originals used a thicker metal and folded it closer together? Is the rebuilt one a cheap job, or that is how they do it now?

I don't want to sell the 69 rad and keep the correct one if I am going to have cooling issues in the future with it, and if it is a better rad, but I would like to put the correct one back in.