Hi I think you answered your Question in the last sentence which equates to not a lot, all these engines were tested to destruction and when they break they take them to pieces to find out what caused the failure, they strengthen the offending part and up the torque/ BHP slightly, if it works well they just keep upping the power to way past the intended production run power, then whatever the engine has achieved up to 45% above the production Torque/BHP if it runs ok they reduce that figure by 45% to the production run power, thats your reliability factor, if you bear this in mind with the age of your car you are just putting more strain on an old engine thats made it this far with no real issues/wear and I bet if it all goes pear shaped and bits start failing he wont want to know unless it involves more money.
Steve.