theres tons of info to be found in the sas build threads. before you go hacking your truck up do some more reading.
and yes you need to have an engine hoop to tie the shock hoops together.
im not too sure what your plan is for the links. square tube with a wall thickness of .250? that would be fine. .250 plate welded together in the shape of a box? sketchy at best!!! your best bet would be to buy some round or square tube and then weld in some threaded inserts like these from ballistic. 7 / 8 - 14tpi Tube Adapters
OR since its a jeep dana 30 just buy some radius arms made for it and just go from there.
imo, if you dont know where to start then you shouldnt even attempt it. buy the big stuff (axle, tires & wheels, coilovers, steering box, etc.) and let a pro do the actual work.
2003 ranger xlt 4.0 auto. 265/75/16 bfg at's, SI/DO super 44 dumped for now, kenwood deck, 6x8" rockford fosgate's up front, stock rears(for now). front reciever hitch blah blah blah. first real mod is gonna be a big one HINT: 14bolt/78 f250 d44 Build Thread Here