There are no cast roller cores for BB Mopars.
Copper color between the lobes is 8620 material.
Black between the lobes is usually 5150 material.
The heat treat goes deeper on the 5150, which allows for more manipulation for putting a wider variety of lifts and LSA’s on the core.
Both are steel billet.
Yes, his was a steel billet but likely (99.99%) it was as Fast said 5150 base. I vaguely remember him saying that Comp would offer him no $break$ for a replacement and they did say that the 8620 SHOULD have been HIS request for his application AND would be a $ upcharge verses the 5150 cores.
