Modern birds are relatively, well, modern by evolutionary standards. My choice in this post was based on conservation of proteins over those millions of years. Basically which modern animals are probably as close as possible to what was available to be eaten 60+ million years ago? Crocodiles are high on the list, helped by the fact that we do actually farm crocodiles already, so that meat supply already exists for hungry dinos.
Birds might be a good next choice, but only wild-type, not modern broilers selected for rapid growth rates and higher fat percentages.
Likely we would need a variety of protein sources, and significant trial and error to determine the ideal nutrient ratios in a reanimated dino diet, but as close as possible to what would have been naturally available is a good start.
What about ostriches? I’m not sure about their protein structure, but that’s a lot of meat and some big bones on an animal made to run. It’s basically a modern Gallimimus. We already farm those.
Would you feed any mammalian meat to the smaller, later raptors, since they likely would have occasionally eaten early mammals?
I wonder if the best option would be to grow meat in vats. If we can perfect cloning well enough to revive dinosaurs, I’m sure we can figure out how to take a sample of meat and grow it in a vat like a weird fungus, like people are already trying to do now.