my 2 cents. since there is very little material in that location on the front of the LD 230/250 block; it would make sence in my mind to install 5/16 studs in the top two holes for the water pump. Make sure to chase the threads first so the stud goes all the way to the bottom of the hole and also fill the threads with loctite or expoxy or something like that to fill all the air gaps. This way the block will behave more like a solid piece when it is pulled on by the head bolt being torqued
although if the studs ever get damaged you will have to throw some heat on it to reduce the adheavsive properties of the loctite to get the stud out.
Michael
