Roller lifters A engine

You have the correct size at 9/32 or "approximately" 0.283 as quoted in the Mopars engine book. They suggest drilling using this size bit in 3 areas: the passages on mains 1 through 4 up to the lifter oil gallery as well as drilling main passages 2 and 4 to the cam bearing journals and drilling the camshaft bearing to deck surface on journals 2 and 4.