i wrote up what all the different combos need as far as plugging goes do search on metal headgaskets under my name, u can plug the extra drain hole and still use that head on a hydro block, it won't make any difference. and if u are just putting a hydro head on a 1.6 solid block with a solid lifter hg, u could actually most likely get away with siliconing the hole shut since theres no real pressures on it.