Dome pistons for 318 stroker

W2s can carry the same casting number but have chambers from the high 50s to full open chambers. You will want to make sure any dome you buy will work with the W2 chambers. Also, if it was me, they'd be gas ported and 1.5mm/1.5mm/3mm oil ring stack. Once you clear 13:1 you'll also need to go to head studs and if it's more than 13.5:1 I'd also get the block O-ringed. In any case, I'd use Cometic head gaskets which means careful finishing of the block and head deck surfaces (ultra smooth... Needs to be done with a modern milling center).