I noted in this months edition of MM&FF the S550 IRS Ford chose to use a cast iron diff housing in the 8.8. I wonder what the motivation for that is. "Heat" and "weight" can't be one of them. The cover looks pretty beefy, is still cast aluminum and has nice widely spaces mounting stanchions. Not sure how thrilled a road racer will be with this as the SN95 all aluminum diff will get hotter than a firecracker after a few laps. Perhaps a diff cooler will almost mandatory as iron moves heat like molasses. Doesn't look like it holds anymore oil either. I think I would prefer this in aluminum just to help wick heat away. Should be interesting to see if the S550 road racers have issues with here.