I cant speak for the other guys that have done this,but I call mine a "one-off".There were no jigs used,it was built on the vehicle.I didnt take down any measurenents as it built on the fly fitting peices as I went.Plus there is alot of different ways and places to locate the pivot points. Some pics
There is a guy in Mt Lake Terrace that will build long-arms (or was) , also we are gonna probably have a "viewing" of a Clayton LA install at Johns shop when they come in if you wanna get a look at a few sets.