In my personal experience, about 40-45 psi seems to be the point that things start to give up. Every truck is different and will react a little differently. If you decide to put more than about 40 psi to it then it's time to start looking at studs and O-rings in the cylinder head. I would stay away from fire rings unless it's a race only truck as they tend to get brittle and break from all the warm up/cool down cycles of daily driving.