I was just thinking that when I came back here to see your reply. I'll need to look at the back of the old 1915 and see what the pressure plate looked like. I don't know if I have a photo of the new motor & it's pressure plate. I bet that's it.
Old pressure plate:
I bet the newer one looks like this:
No centering collar...
The 1600cc had the top pressure top. The old original looking one. The 1915cc has the bottom pressure plate.
I thought the T/O was based not the transmission you have and not the pressure plate??