360 flywheel or weights

I'm trying to help an old hot rodder that lives close to me.
He pulled the 225 from a d150 that has an overdrive a833 and swap in a 360.
He sourced an aluminum bell for the la bolt pattern but it won't accept the 11 inch flywheels he is finding for the 360.
He also has a 318 flywheel that fits in the bell

Is there a weight that can be added to the 318 flywheel?
If not where can he source a smaller 360 flywheel?

The dude is a legit hot rodder who has built lots of stuff but in his 80's he isn't quite as sharp or spry as he once was so it would be nice to help him out.