You will neeed a 318 flywheel if you intend to keep the injection, balance is not a factor as both v6 and 318 are neutral balance, the number of slots for the crank sensor to rear are different and it will not run with a bad crank signal.

You will also need to get a new pilot bearing insert, usually they come when you buy a pilot bearing by it self new but not in a clutch kit. The engine from an automatic will not have the insert ring but you can easily put one in.