I agree with twisted6 if it will clean up at 30 do it. 30 years from now you may want to do it again. By then you'll be able to print pistons at home.

If it were me I would pin the machinist down to where it will clean up. I would have the pistons made and hand them to the machinist before he bores the cylinders or at least do a cleanup bore to fit the pistons. With the '59 270 head flat top pistons are best. Shaving the head & decking the block can add compression. Do your homework and check to see if this has already been done to your head & block. Best Gasket makes a very good gasket set & the best rear main seal I have ever used. Bearings should not be a problem.

"I wonder if God created man because he was disappointed in the monkey?" Mark Twain