328 engine in 318?, you will have obd1 and ob2 problems..if you ever get the 97+ engine that is...
But for the moneywise, putting those engine isnt costeffective these days as the real 325 and 328 aint expensive anyway.
If you decide to gowith engine swap, you will be forced to swap the entire suspension as well. ..
Personally, I would go with FI.