Welcome to the forums!!!!!
I live in Alberta (Calgary) so i know what problems you might have with emmsions and shit. One from the states should be fine, but i recommend getting one from a local dealership. it may be a bit more expensive but since you said cost isnt to much of an issue then its probably ur best bet.
As for the seat motor i cant help to much. But my guess is a motor from another car, say 318 as u said, may work. I can try to find out for you tommorow though.