9/16-26 X double D u-joint is what you want. On e-bay ever day in Summit and Jegs posting and others. Easy to find.
For the sake of clarity, at least in this thread- the correct DD dimension for a 74 pinto is the full 1"DD size?
I would have assumed the 3/4"DD BUT the steering shaft seems to measure 1" across.
I managed to find a reference in Speedway catalog that seems to point at the 9/16-26 x 1"DD u-joint as the right part.
Im gonna order that in a longer looking joint, assuming I will need the difference to get the DD end situated properly.
THANK YOU ALL SO MUCH FOR YOUR REALLY FAST HELP!
I hope I can return the favor someday. If I ever get these headers in I will be sure to share what I am about to learn.