John, you don't use stretch bolts to allow for the head expanding, ALL bolts/studs stretch this is what gives then their clamping force. A bolt will stretch and go back to it's original length thousands of times unless you yield it. The reason they give you a torque figure then an angle ie 265deg is so you yield the bolt but don't break it. The bolt has it's maximum clamping force after it's yielded but before it snaps.
Arp bolts will be made of a different material (obv) and the MOST important part of the ARP bolt kit is the washers and the lubricant, this allows more clamping force (due to grip length changed by the washers) and the lubricant helps put in the same load at a lower torque. Due to this you don't have to yield the bolt hence being able to re use them.
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Boost pressure is underrated
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