Hi bob,there is a lot of experts on this forum ,so I will put my two bobs worth in.i would suggest ringing around the wreckers in Sydney, not far from you? And try to buy a secondhand engine from a vehicle that has had a smash ,but was in good condition with no more than 200 ks. You can usually pick a car that has seen regular maintanence ,looked after and was obviously driving good until the prang.Any engine with the kms you have will really need a full rebuild which you really have to weigh up cost / vehicle replacement/ the real fault to cause the problem. I agree that no 2 piston has indeed picked up on the bore ( scuff marks) and that is usually overheating ,which could have been a long time ago,and I have seen cracked pistons just from age. Ps I have been a motor mechanic for 43 years and still run my own shop,Regards to you