head bolt torque

I agree with dgc333 ...he has nailed it as for the proper procedure. The reason they went to "stretch" bolts and degree of torque is because the old fashion method left a wide variation between bolts when torqued. With stretch bolts you take in a wider range of variables to create a more even torque. Import cars with their aluminum to aluminum and aluminum to cast surfaces have been using stretch bolts for 15 + years.
but for all practical purposes, 3 rounds of torque to the manufacturers spec is sufficient for cast iron engines and by the 3rd round there isnt any appreciable loosening of the prior bolts