2 inch pipe vs 2 1/4 inch pipe

i judt read something on exhaust and exhaust pipe size and it said you want to decide on the diameter of the exhaust pipe size based on what rpm your max torque output is at and engine size. it had a chart with small block and big block dodge engines. I went to the 360 on there chart and it said 2 inch exhaust pipe is ideal for a 360 with its max torque output being at 4750 rpm. My engine puts out its max torque at 4500 rpm. So that is darn near perfecr according to there chart. If you guys would like i could post a link so you guys can see it as well, it was from hotrodders.com. After seeing that i am not stressed about it anymore and will keep it. I'm going to go to my local exhaust shop just to double check its 2 inch exhaust pipe but i am 90 percent sure it is. sure looks like 2 inch exhaust pipe to me.