That block is possibly a replacement block, designed to replace the '58 non-water cooled spark plugs, or it would be correct for th 59-61 348 as well. If you put the later head on it, water wouldn't circulate around the plugs,but it probably doesn't have to. You could drill the holes for ir,use a head gasket for a template. Make sure you know what spark plug your heads need-the '58 non water cooled heads use a short plug like a 283-327, the water cooled heads use a long plug like a 409 uses. Don't ever put the long plug in the '58 head, they will go in so deep that the piston will hit them,breaking and bending them,and you will have to pull the heads to get the plugs out and retrieve all the debris and metal particles in the cylinders. Not a good time.