sliding door latch hardware with double hooks, about 8inches long.

I'm afraid I don't know what part it is you're talking about. Are you referring to one of the parts we sell? If so, can you give me the product code? 

Thank you for these photos, that is a huge help. This is actually a little peculiar. We sell a bunch of mortise locks that are similar in design to this, but none of them have that same white, squared-off faceplate like yours. I've never seen that before.

My best recommendation at this point would be our 82-239. My hope is that you can reuse your old white faceplate with this mortise, as it lacks a faceplate of its own. Look it over and see what you think.

We actually don't make any parts, we're just a third party supplier.

We stock both of these parts, yes. The major difference between the 82-239 and 82-265 is that the 82-265 has a much longer face plate. The 82-239 essentially has no face plate at all, which is why I recommended it for your application.