| Not to rag on you but I've re-read the post 3x and you're all over the place. I understand this: *You have a new (used) crank.
*You need 2 new (used) rods.
*The pistons are good less the swain coating.
*#1 cyl has a MINOR vertical scratch.
*The heads are good. *You are considering machining the main bearings? Are you talking about the crank journals or the block main journal bore?
*You are considering going with new pistons due to the loss of the coating.
Things to consider:
If the cylinders were bored properly the final dimension would account for the overall diameter of the piston which included the coating. In the case of a swain coated piston the coating was designed to remain on the piston through it's service life. Therefore the final bore would have (should have)included this fact. If the coating is now absent then the piston/wall gap will be in excess of that which the original tolerances were machined to.
In the case of sacrificial coatings which some pistons come with and are designed to wear away, the final bore dimension is calculated to exclude this coating and when the motor wears in, the piston/wall gap will be within the design tolerance. Before you buy new pistons you need to know what the piston/wall clearance is now without the swain coating. Based on the recommended piston/wall clearance stated by the piston manufacturer ...or... that tolerance known to be the max allowable for the forged piston with your application you may get lucky and be able to lightly finish hone the block and still be in spec.
So the question you should be asking is:
The pistons look good but the swain coating has worn away. The block and pistons were mic'd and this is my piston/wall clearance. I need to finish hone the cylinders to remove some light scratches and seat the new rings. What is the max bore I can have the cyl's honed to and stay within acceptable piston/wall tolerances, or am I already too far out?
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