Ford Excursion :: 2000 F350 - Vibration That Starts Around 60 MPH

I currently own a 2000 F350 Lariat 7.3 4x4 and a 2001 Excursion Limited V10 4x4. The Excursion has a vibration that starts around 60 mph. What I've done so far...Replaced all 4 brakes (rotors and pads)..

Replaced wheels and tires (I bought new ones for my f350 and put the ones that came off the f350 on the excursion, so I know they were balanced and smooth)
Replaced the front axle (I put a dana 60 on my f350, so I put the front axle that came off the f350 on the excursion... again, I knew it was in good shape with good ball joints, tie rods, etc.)
Had the front end aligned
Finally, today, I replaced the ujoint on the rear driveshaft at the pinion (I discovered the old one was broken).

Through all these changes, the vibration has changed by degree but never gone away completely. Today, I had a bit of a revelation, and would like any input.

It has come to my attention that some excursions were given a double cardan rear driveshaft, mine included, and some had what I would call a standard driveshaft (one ujoint on each end). From what I know, with a standard driveshaft, the pinion should be angled parallel to the transfer case output shaft. However, on a double cardan driveshaft, the pinion should be angled "in-line" with the driveshaft. I measured mine with a digital level and the pinion is angled parallel to the transfer case output shaft.

My only two possible conclusions are 1) all the rear axles that went into the excursions were set up the same way, so the excursions that got a double cardan rear driveshaft are "wrong" or 2) at some point in my truck's history the driveshaft was changed but the pinion was never corrected. Need info on how the pinion is angled?

So finally, my question is, can re-angling the pinion with wedges or by cutting and re-welding the perches to get rid of vibration? Am I on the right track?