What are these Pistons and what's up with my block

So I pulled the heads on my 318 to prep for my 268 cam and speedmaster heads. The pistons are Gold and it looks like it's been sleeved. Pistons sit very flat at TDC and have 4 vlave relief cuts. Bore is just a hair under 4. Let me know what you think will this help with my compression with the addition of my heads and skinny gasket. Gasket that came off looked like a thick composite one.

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