I would only run her a hair over 40psi, unless you want to take all the head bolts lube them very well and then tighten them down to factory specs. After that crank the torque wrench up by 5lbs and retighten them in the same sequence for example 105, 110, 115, 120, 125, 130, 135, etc... until around 140 or so. there are several guys on here that have done this and can hit way over 50psi woth out worrying about the head gasket. Good luck!!