you first need to know the bore size if you make the wall s strait your going bigger so end gaps are going up if cast pistons they will not take the bigger bore .not all hypers pistons need adde end gap sorry i not going to tell you were i put my end gaps but i will tell you check your ring lands that the rings fit good and not all worn out for a carb engine and no Nos you should not need any more then 004.5 pre bore if your more then 0025 then you may what to go file fit but your piston to wall could be way to loose then there is some things i do to get that back were i can live with it by krunling the pistons some look down on this but they do not know one damn thing i done this many times on a $1000 set of pistons were haveing nice round bores this what we wanted