440 what am I missing here?

One of two pistons if they're forged.
Engines & Components Pistons & Piston Rings Pistons DODGE 7.2L/440 Mopar big block RB Mahle Mahle Mahle Pistons & Piston Rings - 4.360 in. Bore (in) - Forged aluminum Piston Material
Hopefully, it's the four valve relief type that would only be .021 below stock 10.725 inch deck. Head gaskets appear to be standard Felpro .051 13.70 cc's volume.