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If you know enough of the history of the engine to know it was not using a significant amount of oil then it may be OK to use the old rings. The key is the end gap of the rings when they are installed in the engine. There are minimum and maximum dimensions.
No detectable ridge, at the top of the cylinder, is a very good sign that the ring to cylinder wall tolerances would be good.
Slip the top ring (after you carefully remove it from the piston) into the cylinder. Use the same piston (inverted) to push it down so it (the ring by itself) sits evenly in the cylinder, from the top. Take a feeler gauge and measure the gap where the ends of the ring meet. That is your end gap dimension. There should be specifications for the end gap,something like 14 thousandths (but check for the proper spec) If yours is within the allowable tolerances, especially towards the minimum, the wear is minimal.
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Most important, you must know this without a doubt
If the engine did not burn oil (if you can verify that) and if it did not run hot (also if verifiable) then you should not have a problem. An overheated engine can cause the rings to loose their spring tension and not seal properly, even if they look fine.
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The greatest amount of wear in the cylinder walls will be at 90 degrees to the piston pin location. The piston pins line up with the length of the block, so the greatest wear will be on the sides (if that makes any sense). This is because the pistons suffer the greatest side (same point where the skirts extend from the bottom of the piston) loads when the connecting rod is turning the crankshaft in response to combustion pressure.
Also you want to check the top of the block to make sure it is flat, as well as the mating face (bottom) of the cylinder head. This will ensure you do not prematurely encounter a head gasket leak after all the time and effort to put it back together.
If the head needs to be surfaced to get it flat, the amount of warp-age needs to be minimal. or you could have to surface both sides of the head and use cam tower shims to get the tolerance between the crankshaft and camshaft back to its original specs.
While you have it apart I would have the intake manifold chemically cleaned to get the goop out of the EGR passageways. It wouldn't be a bad idea to have everything cleaned professionally.
The machinist is a key component in your eventual success. He can give you invaluable advice on what to make sure you have done to get the max life out of the engine.
Show him the pistons, main bearings, etc, and get his opinion on whether yopu really need them or not. On the other hand beware of those who will sell you stuff you don't need.
Many here who are more familiar with the 1.0 engine you are working on can give you more specific advice, and there is a world of info on the net.
My best advice is to take your time and research the best info. Knowledge is your best insurance of not having to do a repeat, and when she is purring like a new motor the thrill is priceless.
Take pictures of things before you tear them apart to help you get it back together correctly since it is your first rebuild.
The thrust bearing is usually one of the main bearings. It sees pressure when you push the clutch pedal down and the throw out bearing presses on the pressure plate. That same force is trying to push the crankshaft out of the front of the engine. The thrust bearing face will always point to the flywheel end of the engine.
regards
Mech
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