The head looks in very bad shape, but the piston doesn't, so that would suggest to me that the damage on the head was from a previous disaster. It looks as if the ring broke then did the dance around the conbustion chamber. It's not normal detonation.

I haven't done a huge amount of MC16 work (practically none actually), but I have offered up MC28 pistons and cylinders and it looks as if they'll fit without any trouble at all.

I can't say the cylinder will be all that much better because what I was dealing with was just an MC16 bottom end, but the 28 piston's a better choice because of it's crown coating, compared to the MC16 that's just plain aluminium.

There'd obviously be a few plumbing issues by fitting later model top ends, but I doubt that it'd be a major headache if you were willing to do a little research to find hoses and stuff.