You have to sonic test them. The fact they used the 340 cores is right, but the few I've tested ('71 cast 360s) had too much core shift so the bore was thicker, but the meat was in the wrong places to (by my definition) safely allow for larger overbores than .040. It also depends on what your expectations for the engine are vs what the minimum thickness is. I also think by the '73 casting dates they had thier own cores and were not using the 340's. Remember the 340 was killed by corporate decision well before production stopped so they had already tooled up for 360-specific production.
