I'm looking at rebuild kits and some say they have certain things undersized or oversized by so many inches. IS that for if it is strocked out or if you want to stroke it and increase the ci? I plan to go with the stock sizes though but I wanted to know. Thanks

 

That probably talking about bearings. You might need different size bearings, for example if you have had your crank ground down, you will need oversized bearings.