I have a green S45 with a replacement motor. I bought it used from a guy that had a custom aluminum adapter plate made, so I can't help with the specifics in your case. I think he bought it used and replaced a 3-phase motor with single phase.
The motor that came with my saw was a 3hp 3450 RPM motor. It ran way too fast in my opinion. I swapped it out for a 2hp 1725 RPM motor and am much happier. I forget the exact calculations, but it brought the speed from around 4000 fpm down to around 2000 fpm.
Steve