Hi,
First of all, the PM80 (lol at Speedmatic, but I knew what you were saying) DOES have a plastic pallet AND plastic escapement -- no thanks!! I just verifed this by re-reading.
Next, you CANNOT do a mvmt swap or low beat mod to a Miyota!! The hands will not work, the DW doesn't either, mvmt tabs won't line up, and as I recall I think even the dial or dial feet will cause a problem too. This paragraph is from memory - but there are definitely issues & I believe those are the main ones!
Buy a Diver with 2824 mvmt if you want to do ANY mvmt modding!!
This is info posted from a VERY prominent member & a friend, I didn't figure it out and taking no credit - simply repeating it. Take it as 100% true though!!
Good luck!