Engine out, and then split the crankcases. The first time I have done this on the 350. Lots of crap in the bottom of the crankcase, but luckily no damage to the crankcase, however the con rod has bent, so the crank will definitely have to be rebuilt. The cylinder is also marked quite deeply, so waiting for the advise of an expert to know if I can rebore successfully. It looks like the bearing on the Rhs has spun a little not sure if any of this would have been a cause of the trouble.