I've used both of these in a '80 M-body coupe (Diplomat):

1) #78050, Headman Headers
2) #5901, Hooker Competition headers

Both were 1-5/8" primary pipe diameter. I liked the Hooker pipes better...the flange was thicker and perhaps the tubes as well. They were heavier w/o a doubt.

For my W2 stroker build I selected:

TTI #340BEW2-17835C0 , 1-7/8" primary tube, un-finished, 3-1/2" collector

...but I haven't tossed the combo into the car yet, so no hands-on fitment results to report.

FYI - I have long time ago gone the route of the Lokar cable setup for both throttle and kickdown, so I didn't have to make some of the adjustments to the support/pivot rod that I remember doing in my first Mopar ride, that being a '78 Plymouth Caravelle (M-body, Canuck).