Ported X head 340 header size?

Oldmanmopar said
If your using factory heads 1 7/8 for a 202 208 valve 340. 1 3/4 for a 188 valve 340-360 or a small cam 202. 1 5/8 for a 318-273.

I like this though on a more conservative engine, I move the pipe size down on on the valve size. This should be a chart for the heavy hitter like street car builds.