Best Piston Rings for the Magnum??

Poly? (probably Moly)
The OE 5.9 rings are Moly (chrome moly).
If you have new aftermarket pistons you should ask them for specifics on rings, like material, and end gap requirements for boost.

lol yes thank you, I reread this post like 5 time and never caught that... Moly rings
No stock magnum pistons, so Moly it is...
thanks