318 combo's

1973 dart 318 /904 and 355 gears eventually, has 2.94 now, stk converter hooker super comp headers and offy 4bbl dual plane intake. any you have any 318 pistion size recomendations? stok 318 strock and bore, with 340 purple cam and stock 318 heads with eldy valve springs. looking to rebore with new pistions, can go higher on compression and size with 318 head, any suggestions? also will be uniing m/p higher compresion thin head gaskets.