I don't live in OKC but there was a huge diner that sat on a hill looking over the city. Seems it was called Skyview or something similar but that might be totally a guess. I took my kids there when they were teens so 15 or so years ago. The waitresses all dressed like Flo, ours even looked like Flo, and the menu had every diner classic you could think of, including my favorite from up north that's not as common here, an open face roast beef sandwich covered with mashed potatoes and gravy. The kids hated it but I loved it. I'm into nostalgia.
Sounds like the Skyline on SE 15th just to the east of I-35. It's been gone for quite some time -- seems like the building is some type of oilfield or trucking operation.
.