Sorry I didn't mention that is was a Jag IRS - and there's no C notch. It was narrowed about 3" side to side and tube steel half shafts replace the Jag's forged half shafts.
The ladder truss supports the differential and is mounted on urethane bushings. The bolt that hang the diff in the truss are about even with the bottom of the wood boards in a stock bed.
This bracket assembly holds the differential assembly in position and keeps the pinion angle constant
The airbags ride on a trailing arm that connects to the Jag's LCA. It is a 5" Slam bag that does the same job as the Jag's coil-over springs.
Another photo
The front of the airbag trailing arm - it has the same roll center as the LCA of the Jag IRS
And yes. a four link and a c-notch would have been a lot easier. But it's all about the nostalgia of the Jag rear end