probably best to 'glazebust' the bores - think any haynes manual covers this.

trust the bores aren't too worn. the thing that can be a problem is that if you have a lip at the top where the original top ring was at TDC, then if your new rod/piston combo puts the rings a little higher owing to manufacturing tolerances, then the new ring will hit the step and get damaged.

this problem can also happen with rod stretch, for example you buy a car off your granny/ sister whoever that has never been run past about 3k, and first thing you do is take it to 7k. the extra revs stretches everything past where they took it and you hit the ridge.

fortunately my granny doesn't drive any more (just as well) and when my sister isn't looking i make a point of taking her car out and thrashing the living daylights out of it just to prevent this problem.