Chasing threads is a pretty standard practice. You get a tap (thing used to thread holes for bolts) of the same size and pitch of our headbolts and you thread it into the holes (and keep adding oil to lubricate and clear out debris). As you thread it in AND as you thread it out it cuts the metal of the threads back to the right shape and size for the bolts/studs. Not doing this may cause the bolt to reach a given torque level but not provide the actual axial clamping force you want (ie: the shit don't turn so easy so you think it's done too soon).
I really wish they made hollow studs for our cars.... that's the only way to get really close to a given clamping force. Hollow's are great.
Yes, the headbolts are reusable.
80lbs is high... don't go over manufacturer specs just becaust you think it'll be better... you'll break something.
Also, rebuilt of not, you don't know what shape the head was in... could have warped from inappropriate storage. Measure it with a machinist's straight edge (not just a metal ruler!
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