History Help Identify These Old Silv-O-Lite Pistons

I bought these pistons at Carlisle one year on a chance they might fit my 330 Desoto. They appear to be Hemi pistons with the valve cuts, but they're definitely NOT for the 330. They measure 3.935" and have Silv-O-Lite cast into the inside of the skirt. They are STD. size, as stamped on the top of the piston. There is also what appears to be an "8", along with "8063P" stamped into the top. The fellow who I bought them from said he had the box at one time, but it fell apart after a few years of hauling them around.

I'll include a few photos to help illustrate. I have a complete set but don't know what they are for. I checked (Google'd) for the numbers on the inside and couldn't find anything. Any info is greatly appreciated. Here are a few pix.

 

'56 NY - Imperial 354 ...

 

Holy cow! That was fast!

Do you have an old parts book 302GMC or am I just a Google-diot? I DID look for it. I promise!

 

I looked in a '56 MoTor flat rate for bore sizes.

 

Thank you!