Swapping 1970 hood cat?

So, I have an insert, that is not broken, missing the cat, and I have an insert that has a couple of broken ribs, with a good cat attached. Before my original one broke, I figured it just had pins in it, and now know that is not the case. How do you remove the cat, so you can reuse it, and then how do you secure it once it’s off?

Just did mine to replace the backing behind the cat. Basically you have to grind off the back of the pins and then get creative on re-attaching the cat either with some solder or epoxy.

Anything better in today’s world besides JB weld for this kind of thing? I have heard some good things about a 3M product-