Torking the head bolts to 45/50 lb/ft of torque requires only a grade #5 bolt, unfortunatly these have 5/8 heads, the grade#8 have 11/16. When installing these in aluminum heads a hardened washer should be used and the bolts/studs should have a minimun of 7 thread engaugements. You must check for bottoming in the blind holes in the block over the exhaust ports. Caution torquing over 50 ft/lbs ann distort the block and is unnecessary.