I don`t know anything about Fidanza products, but both my McLeod Soft Lok, and current RAM Billet/ Black Magic Defiant clutch use aluminum flywheels, and the starter ring gear looks to be an OE style piece, with 3 tabs welded to the edge of the ring gear, and bolted or rivited to the aluminum flywheel. I imagine that is due to the different expansion rates between the aluminum flywheel, and the cast iron ring gear. The steel McLeod flywheel on the 428 in my 59 just a friction fit, like a factory cast iron flywheel.