2 1/2" vs 3" system

At what point do you go to 3" over the 2 1/2" pipes ? I would believe 2 1/2" is enough for a 318, but is that enough for a 340 or 360 ? For street driven street/strip type cars. For dailey driver I would think 2 1/2" is plenty but if building a very high performance 340/360 or even a stroker would a 3" system be needed ? Your thoughts please and thanks.

Terry