[bama63]

i have ran them on the local dirt tracks in all stroke combination's from 352s to 434s and have had no problems,just like any engine a good clean cooling system and adequate air flow and you wont have any problems as for drilling the steam holes in the heads if you are in a lot of heavy traffic then yes if you mostly drive freeway then no i personally have used them both ways and saw very little difference in temps with only a slight 10 degree increase if idling for a long periods and you also cant go beyond .040 overbore unless the casting is perfect when sonic tested