My original flywheel was iron. I have no way of knowing if it was "original" to the car but it was date coded correct so I will ASSUME it was the original flywheel. Anyways it's probably been melted down and turned into a Corolla by now..
I have a LUK in my small block, they're popular with German cars. I've had good luck as well.
I have McCleod in my 396 and 496. Work GREAT! I chose McCleod because the clutches are made in USA, however the iron flywheel could be offshore
I have no experience with Centerforce.