Lightweight flywheel options and selection criteria.

The lighter your flywheel the deeper the rear gear you'll need to run, or it'll fall flat on it's face when you try to launch. If you need to run a semi street-friendly gear, you can get by with a middle ground flywheel. Highway gears, heavy flywheel.
Stay away from aluminum flywheels that don't have a ferrous friction surface (not sure if they even make those anymore, maybe I'm dating myself...)
And definitely yes to a scattershield (with block plate) if you intend to turn some RPMs with this thing. But if you weren't intending to do that, you wouldn't be building it this way and we wouldn't be having this conversation.