I think the trans mount was the same for many years.
Reason I think that is I used a '69 B mount in my '63 Savoy when converting it from 3-speed stick to A833.
I used the same part when converting my '64 savoy from 3-speed stick to A727.
Could be a '62 is different as there are a lot of parts unique to them.

Oh, and I believe a 60-62 Plymouth A body would be the Valiant, though technically it wasn't assigned to the Plymouth line in '60.
The 61-62 Lancer was the Dodge equivalent to the Valiant, of course.