The 390 truck engines used the 410 piston and the 410 is prominantly stamped on them. Passenger car 390 pistons, 2V or 4V, are 1.76 or therabouts compression height (the 390 4Vs being also used in the truck 360s), 410s and truck 390s are 1.66. That's how they lowered compression in trucks without stocking new pistons.