Doug's headers (D453) install/fit questions

I'm getting ready to bite the bullet and install some headers on my 69 Barracuda. (360/904, floor shift, and Power steering). I am looking at Dougs (D453) but looking at the description page on Jegs, it says they will not fit with a 727. (That note is not on the page on Summit's website... ) It just so happens that I have a 727 that I was going to install in place of my 904 (904 is getting tired)... So, question is, has anyone installed these with a 727 or know what the issue is?