I have run the conversion joint for a long time, no real issues (my issues are with axle wrap). The only thing that sucks is the joint is expensive and most parts stores take a day to get it.

Also on your sterling, make sure it is actually a 1350, mine is a "1330F", a 1350 is wider from cap to cap. A 1330 has the large caps, but is the same width cap to cap as a 1330. Ford did this a lot.

Also, your 1356 to 1356 doubler, you got an extra 1356 for it?