408 build help
This is what you want to look for on both banks, between cyl 1-3 and 6-8. Oil passages drilled. Early Magnums have the passages drilled. At some point they were no longer drilled, hard to pin down exactly when that occurred. But just because it’s a Magnum block does not mean it’s not drilled. You may luck out, and will then have more options for rocker arm assemblies.
This is what you want to look for on both banks, between cyl 1-3 and 6-8. Oil passages drilled. Early Magnums have the passages drilled. At some point they were no longer drilled, hard to pin down exactly when that occurred. But just because it’s a Magnum block does not mean it’s not drilled. You may luck out, and will then have more options for rocker arm assemblies.