Somewhere I remember reading that the two holes in the middle where the bellcrank pivots give away that it is magnesium. Too lazy to go look it up to verify. A&A transmission is a good resource btw they repop the crossram in aluminum. Painted my magnesium crossram in Hemi orange to match the motor. Also have a Weiand aluminum vintage Hemi tunnel ram with two new dominators and the vintage chrome Holley airhorns that I bought on a whim and now functions as an expensive garage paperweight