That piston damage has been caused by the engine swallowing a metallic object...
When an object thicker than the deck clearance is swallowed, it will and does cause the piston to be subjected to excessive stresses.
The piston is most likely cracked through the pin journal area or the skirt area....
A 350 that is already plus 040 has one rebore left...up to .060 over, without going to special size pistons...= more dollars....
However, the cylinder walls get very thin at .060 over....
Is this engine a roller cam engine or a flat tappet cam engine?
Is the engine a 4 bolt main or 2 bolt main ?
What is you expected use for the engine?
Have you removed the piston and rod and checked the cylinder walls for damage?
If its a flat tappet, 2 bolt 350 already at +0.040....it has a future as a street engine...others may disagree, but after building well over 300 of these small blocks over 35 years, you tend to have an informed perspective.
I hope that bike you traded was a el cheapo...if its a 2 bolt 040 over 350, its worth $150 max, especially with a damaged hole...
