Aluminium Flywheels
I honestly can't recall a flywheel weighing that much.
90 pounds is 3 stock flywheels!
For the record, my turbo build will have either a aluminum flywheel or a lightened steel flywheel.
Anyone can run one but just remember to compensate for the lack of inertia when starting off. I don't think a stock (read-underpowered) vehicle would benefit in any way from a light flywheel. You would probably lose some momentum at shift too, compared to the heavier stock flywheel, and you would not have the power to overcome that loss.