SD Anamorphic files

Hi! I have a bunch of files digitized from PAL Anamorphic digibeta tapes so the picture is squooshed. I need to unsquoosh it. 

I found helpful directions online BUT when I use Media Encoder to convert the files to progressive and expand them, for some reason it keeps setting the display ratio to 1.85 instead of 1.78 and I do not have enough technical understanding to know why or how to fix that. I tried setting it to "custom" and entering in 16:9 manually but then I wind up with a file that displays as 2.23 (super stretched). 

These are the settings I'm using:

• Format = quicktime
• Video Codec = Apple ProRes 422 (HQ)
• Field Order = Progressive
• Aspect = PAL widescreen
• 720x576

Thanks!