440 what am I missing here?

All the more reason to switch to an Edelbrock performer rpm. Optimal rpm rating of 1500-6500 (keyword is rating, YRMV) as opposed to the 3000 to 7500 rpm rated manifold. You had also mentioned the possibility of fabricating headers for it. I’m curious if Andy thinks it would be worth the trouble and if so what size & length of tubes would work best.
That was gonna be my next question? I am gonna call comp today, and see on a cam. I think with that head design 1 5/8 is the largest header tube I can use,and still bolt them on. I could step them up to 1 7/8, or 3/4 but I don't think that ever makes a difference. I also will have to physically lay them out to figure out lengths, and that is generally up to the truck,and the space I have. Sounds like I should see what comp says they might have something that will work great with the exhaust the way it is.