I've done the conversion from closed to open driveshaft on my 54 AD. The closed diff to open diff conversion and to relocate the open diff. to center the wheel in the wheel well, requires nothing more than a 6" piece of 1/2" thick X 2" wide flat stock. I drilled a hole on the bottom of the plate that fits over the stock spring pack bolt head and then went 1-1/4" back from that hole, on the top of the plate, drilled and tapped a 5/16" hole, locktited in a bolt that fits inside the center hole on the mount plate on your open diff. This moves the diff back to center the wheel in the wheel well, and when you u-bolt it all together it sandwiches the plate. I also removed one lower leaf from the spring pack. I could/should have gone with a thicker plate to lower the stance on the rear axle. I've got some 1" thick plate which I will weld to the 1/2" plate. At the time my u-bolts were too short so I got in a hurry and only went 1/2" thick.
I found that Autozone has a "lowering kit for the longer u-bolts....you don't want to use their flimsy aluminum block. One word of caution....don't do anything about your driveshaft until you've got your diff all secured. Moving the diff to the rear 1-1/4" does NOT equate to adding 1-1/4" to your shaft. Not quite sure why, but WAIT UNTIL EVERYTHING IS BOLTED UP, WITH FULL TRUCK WEIGHT ON YOUR SPRINGS TO MEASURE YOUR DRIVESHAFT.
I've got some pictures of the conversion on page 6 or 7 of my webshots "shoebox". The full cost of the materials for this conversion were $24. for the AZ lowering kit and a couple bucks for the plate. I used the stock shock mounts and u-bolts from the original diff.(no modification needed) Installation took me a couple hours. I retorqued the u-bolts after a couple hundred miles...works like a charm at 1/4 the price of a mail-order relocation kit. Hope this helps.
