I am not saying a magnum block is a race block but it is a simple fact it is much stronger than an LA 360-340-318-273 except possibly a 340TA block. I made a big thread showing some of the differences I am aware of and they are not insignificant.

As for detonation tolerance I am running 11.5 with stock ported by me iron magnum heads and a tiny 221@.050 cam 91 octane and ZERO sighns of detonation, try that with some dinosaur open chamber LA heads.