If you're putting on a MHG you MUST machine the block and head to the proper RA spec for the brand of HG you get. When you machine the block, make damn sure you've got the lower backing plate bolted on when doing so (can't remember the actual name of the plate).
If you don't do this, you might as well toss the money you spent on the HG down the toilet. Do it right the first time.
Get new head bolts/studs, preferably ARP studs. Torque those down to 81 ft/lbs. w/moly when installing. Don't spray ANYTHING on the new MHG, it's got it's own sealant on it right out of the package.
Make sure the bottom end is in good shape while it's outa the car for machine work. Do the same for the head, check the valve lash. Go ahead and get a new timing belt as the old one could be stretched (I think either GReddy or HKS makes the best one out there for our car...).
Do not start upgrading the car with performace part until AT LEAST all of this stuff is done, or you will be parked in the driveway for an extended period of time
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Hope this helps! Didn't mean to rant BTW.