I would buy or borrow an inside mic to measure for cylinder bore taper (top compared to bottom), then if it is acceptable, put in a new set of standard rings.
I wouldn't worry about the accidental intake valve recess in the piston/block. I think that the area of the dent in the block will have enough head gasket surface area to prevent blowing out the gasket. If it should fail (unlikely), you will know before catastrophic failure occurs. Your only other preemptive choice would be to find another block.
Carl
