Here's pics of a 352 piston modified for a 300. In this case a CNC program was set up to machine a mirror image of the combustion chamber in the top, as lots of CR was desired. For most apps it is simply necessary to take off .050" from the top.
I much prefer the (4.000) 352 over the (4.050) 390/361 piston. 4.050 leaves very little for clean up rebuilds and weakens the bores.