318 Pistons: baffled

Not sure which site that is, but the Silvolite 1266 is a floating pin 318 cast piston. 1.741" CH. The Summit description says pressed pin, but that is because it can be pressed into press-fit rods as an alternative. But you can see the groove in the Summit pix, and the Silvolite catalog clearly states it as being a floating pin piston.

http://www.summitracing.com/parts/uem-1266-std