What caused this damage

i will try to get some pics before i go away on 2 weeks vacation ob sunday

the hole on the other side i think is because the rod hit the pickup and the pickup made the hole, i also think that they reved the engine to far but i cant say how far before i get home from vacation,it was no problem to get that piston out from the cylinder,it was like pushing out any other piston,the people that built it told me that the first time they dynoed that it gave to much hp so they did change the pulley to get it down to 6 psi for the light hot rod and that is how it has been driven on the streets until the damage.

And there is no dampner on the engine,dont no if it was balanced but i assume because it was serious people that built it,they drive dragrace, 7sec 402m

allt the other pistons look like new out of the box.

My plans for this engine is only a cruise/street engine,i will take the crank to a good shop i know and look so its good,buy new h-profil rods and good light weight pistons and find a new 440 block that is a little difficult in sweden and put a girdle on it as you say,i also think the rev took it,what is the max rev of a engine like this? 5000-5500rpm.

The bore was 0.06" and is that ok for a mild blower engine
compression ratio was about 8.7-8.8,little to high or good with the aluminium heads.
I have been reading a lot about mopar bb blower engines and some people say that you dont need a dampner and other say you need a dampner,that is pretty confusing,hopefully i can get a couple of pics tomorrow.

/Petri