Actually, moly rings require less surface roughness to seat. And to the OP, the factory moly rings are CERTAINLY a factor in why the engine has lasted this long. They are easier on the cylinder walls than plain cast iron rings, much easier than chrome.

File fitting is great, but you still have to deal with the taper in the cylinder. If you have 0.007" taper, for example, it will be on the top end of ring travel. But on the bottom end of ring travel it may be close to standard size. So if you gap the rings properly at the top, they may have problems a the bottom of the stroke.

Total Seal rings in standard size sound like a good crutch for this engine.

R.