Can I swap one set of .030 over pistons for another, without machine work?

I have done it, I removed my High compression domed pistons for a flat top with valve reliefs. I did replace the rings, and made sure the ring gaps were correct. If you were boring the block 30 over, it is recommended to measure the pistons, and bore each cylinder to fit the piston with the proper piston to bore clearance. It depends on how "critical" you want to be and if you are into balancing and blueprinting. I am pretty sure that a matched set of pistons will be really close to being the same weight.