Could anyone help me ID dining chairs? Borge Mogensen?  

They look like the Borge Mogensen Model 122 dining chair
You can get them here:
https://www.1stdibs.com/creators/borge-mogensen/furniture/seating/dining...
I believe you may be able to get the reproduction from https://emfurn.com
We buy custom reproductions from them for our design clients often so they might be able to help you out.

Those are not Børge Mogensen's SM 122. The stile tapers below the backrest. The SM 122 does not. Also the side stretcher is too high. Early SM 122 did not have a stretcher at all. Later the stretcher was placed down lower.
Catalog pages for '58 and '54 attached.
It is possible that it might be a Mogensen design for some other company. He was known to re-trace his own footsteps from time to time.