First, to answer your initial question--you will need oversize rings to match the oversized pistons. There's been a mixing of mm and inches in this discussion. Derek's figures work when you realize he listed the oversize at .020 (inches, I presume) and the metric diameter at 88.6something. You have pistons at 88.9something mm and they are stamped with 030. I'd say your oversize is .030 inches. Chances are you'll be just fine reringing it but for peace of mind and not much cost it may be wise to run the block, pistons and crank by a machinist for accurate measurement of bore taper, journal roundness, etc.