The piston manufacturer should have a recommendation for you as to bore size.
I think 700 or 750 would be the same for clearance since they are manufactured the same.
I've been using Tech Line PowerKote CBC1, which is a ceramic coating with good results. I apply it to the piston crown, combustion chamber, and exhaust port, and I notice a definite difference.
No recommendation for the skirt coatings though, but I'm interested in hearing for any recommendations for that.