Oil ring's along with Cylinder Bore is also Detoriated it cant be a reliable fix if only ring job is done. You had to rebuild the complete engine with following parts.
1: Oversize pistons 0.50
2: Oversize ring's 0.50
3: STD Main crankshaft Bearings, CON Rod Bearing's , And Thrust Wahsers
4: Head Valves STD Size Along with STD valve guide's
5: Fuel Pump Assy (IF Required)
6: New Timing Chain and Chain Tension-er.