I mean like from cast to forged. I have never balanced any of the stock rebuilds I have done and have done plenty and never have had a problem. The only engines I have balanced were ones that I went to forged pistons with different pins and the rods were changed or polished. Oh and as far as putting everything in little baggies, is there any other way.

well  when i pull the piston  i  put the cap back on the rod with the nuts,  but  yea  if  you weigh everything when you go back  many times a set of pistons from the same box  can be as much as a gram off,  i have built motors  that i didnt balance  for one reason or another, like the one im running now  and  its just not near the motor  my previous motor that was balanced

i always  balance