I'm not sure, but I can tell you that there ARE at least 2 sizes of flexplates. My Riviera has a larger flexplate than the Regal. I'd measure them to make sure. Otherwise the starter won't engage. Don't ask me how I know this! LOL
The flex plates are the same. The mass or external weight is biased towards one side the same. What I have noticed is some of the older (say 84-85ish) will have turbo stamped into them. The NA flexplates will have rivets to add weight. The turbo flexplates wont have anything. If you are doing an engine build and having it balanced, then a NA flexplate will work fine.
I had an 85 turbo Riv engine and the flexplate is also the same (160 tooth) as the 78-87 Regals.