just measured the sb arp bolts and the stock head bolts .. approx 3/8" difference. arp bolt # 144 - 3602. so it appears stock bolts have more thread length and gripping forces.
Also , what did you mean by this Quote " I think I'd run stock 273 head bolts at 85 ft lb anymore, maybe with hardened washers. " ?
and yes these new Arp bolts were loosening up some bollts as much as a 1/4 turn on the torque wrench before I disassembled the 273. still have NOT found the smoking gun yet.