here is a link to a video that shows installing an s10 rear axle into an AD truck. it has some good info and a how to on the whole thing, including relocating the axle center line to the correct place. they make their own adapter. I would use something other than a nut welded onto the adapter plate or do something like drill through the plate, slip a short length of round bar half way into the hole, and plug weld from the back side so you could grind it smooth and the round bar protruding from the top side would be a good fit in the axle bracket with no welding protruding on the top side. then when its all assembled and bolted up weld the bracket to the spring pad.
one thing to remember when grinding and welding on axle tubes is to keep the amount of heat to a minimum. axle tubes can be bent from the heat applied to only one side of the tube. trust me on this. I have had to repair a few home done jobs. usually it means getting another rearend.
https://www.google.ca/url?sa=t&sourc...AiiNoLjfG9EHlL
here is a link that shows the rear axle conversion kit that is supposed to work with the open driveline conversion. if you do make your own it is a matter of getting the hole in the axle spring pad in the correct spot so the axle lines up in the fender opening correctly. personally, I like to mark the axle at the centerline of the spring perches, then assemble it all without welding the perches on yet. do the u bolts up just enough to keep it all assembled and in place. then do the driveline angles and check centering before tack welding the perches to the axle. then take it all down and do a good weld on the perches to the axle. that way there are no "oopsies". you need to have the truck weight on the spring as well. like a simulated ride height. you will also need to make up some shock mounts at some point.
welders series has lots of fabrication brackets etc. their parts are quality and they are Canadian so shipping is pretty quick.
https://welderseries.com/?_vsrefdom=...waArqbEALw_wcB