Ported X head 340 header size?

340s like to rev. Use the 17/8 headers specially if your heads were ported by Mullins!
Yes, these heads are beautiful. Thanks for one more vote for the 1-7/8”s. I’ve always felt a little guilty about not really using them more fully. The next time they are off I’m getting them to a flow bench to see what they really do.
Years ago when I first had the seats touched up, the machinist said, “Man, somebody really broke the bank on these heads!!”
(long story about how I came to have them. ...And this block, which has the cross-over oiling, and other work, done by Larry Atherton’s shop.) Piece of history!