I had my 272 rebuilt last year. bored to 292. zero decked block. Added forged pistons from Mummert. Also rebuilt a set if 1957 G heads from F100.
After about 1000 miles had to pull the motor.due to ring land failure on no.7 cylinder. Piston was damaged. Also had slight head gasket failures in each head. 
I did have a problem with detonation but corrected that with timing. I am trying to understand what caused this.   
 
  

I think you hit the nail on the head detonation or preignition as some people call it will do a lot of damage to an engine if not taken care of . Timing or a higher octane fuel should take care of the problem there are many reasons for detonation a feathered edge of a valve ground wrong can detonate the fuel premature or a electrode on the spark plug glowing can cause a problem I do not know how long you had the problem before you did take care of it but I guess it was to long. 

What do you plugs look like.. Are plugs very 'clean' is there little black or silver specks on the porcelain? It would give you an idea of how bad it may have been causing the problem  ...



"Came too close to dying to stop living now!"

Hi, how much deck height are you running?, also what head gasket are you using?, 

Along with the previous suggestions for fixing the problems. Are the gasket leaking "G" heads milled & how much? Early unposted "G" heads have thin decks and should not be milled much more than 0.025" according to Ted Eaton.  Also, if you are by chance running a Ford 57-58 distributor, according to John Mummert, those years have more centrifical advance than desirable, & were entended to be set at about 3* initial those years . When you add in higher initial with a performance cam, which is usully the case to get it to run decently, it can result in a serious problem.   


Paul

I adjusted the timing as soon as I heard the pinging. Of course this was when I had the motor under a load on the highway. Mostly driving around town so I did not notice pinging.He did a skim cut on the heads less than .010" ( we discussed this before he did the work. (Isky 301444 cam  , MSD distributor, 9245b intake, 600cfm carb)

   I have taken the motor back to the builder for him to tear down and analyze further