Problem With McGaughy's Drop Spindles on 67 GMC

[fasttech]

I purchased a McGaughy's drop spindle and 13" brake kit (#63148) about a year ago for a disc brake conversion on my 67 GMC. The kit #63148 is supposed to be specifically designed for 60-70 Chevy / GMC trucks. I called McGaughy's a few days ago and they confirmed I have the correct kit and it should just bolt in. I finally had time to start the conversion and now I am having a problem with the spindle working with the upper ball joint. Basically the hole in the upper spindle is slightly larger than the stock drum spindle I took off the truck, and as a result it never seats on the tapered shaft on the upper ball joint. The upper mounting point on the spindle is also a lot thicker (1/2" more) than the stock spindle. The strange part is the stock lower ball joint and tie rod end both appear to work just fine with the McGaughy's spindle.

When I try to torque down the castle nut for the upper ball joint it just keeps going way past the cotter pin hole until the top of the spindle runs into the bottom of the upper control arm. So much for just bolting right in! The stock upper ball joint is 1/2" at the threaded end. The bottom side of the hole in the upper ball joint mounting flange on the new spindle is .56" or 9/16", so it looks like a ball joint with a 9/16" threaded shaft might work. Any one know the threaded shaft size on a 71-72 upper ball joint? I don't have a problem changing the upper ball joints if that is the solution, but no parts stores have these on the shelf anymore that I can try before I buy. It will be a special order or on-line purchase so I want to make sure changing the upper ball joint has a good chance of working.

I am not a fan of McGaughy's stuff so far. What should have taken a couple of days is now turning into weeks!