400
To see what is required to add life to the head deck of a 400, you may want to check out the old Bill Jenkins smallblock chevy engine building book.
It details how to drill, tap, and plug the steam holes. It also shows to add plugs with holes in them to the big water holes in the deck and mods to other water holes.
I followed this once and the 400 block lived 7 full seasons of drag racing. It eventually cracked from a head bolt hole to the bore. Rest in Peace.