I would always retime the motor. The length of the leg on the rub block may be different from the points that were in it before. This would cause the points to open and close later or earlier depending whether the rub block is longer or shorter. Plus, even if the rub blocks were exactly the same length, new points are going to open later and close earlier than worn points.
Plus, there is nothing more fun than trying to find the TDC mark on a dirty, greasy flywheel in a dark bell housing while wearing bifocals.