Machining a block, how it´s going???

A good machinist will want the pistons so the final clearance will be in spec. Have him measure the bore so you can choose the appropriate next oversize. If it's std, you're likely good to .030. At .030, you might get away with a .040 piston.

Yes the wall must clean up to a size before honing would be my suggestion. I'd ask what size the machinist might suggest to get a fresh wall surface.

Not all .030 over pistons are the same size, they vary slightly and the type of piston will also determine total clearance. I have a set of KB107's that the bores had to have specific pistons in them because of size variances.