help with crossmember & rear ID

[zicc1835]

need some help I see drawings of the rear and the pan hard bar bracket welded to the rear housing in shop manuals like the pictures that were sent to me.... are they specific to year or weight class c-20s or 30s and the crossmember with the bent out cut out for holding the brake line . I believe you can also make out the filler plug in the front of the rear sometimes called a corporate rear like my 67 3/4 c-20 had in it, not a 12bolt. My chassis the one I'm working on presently , is a 72 and the c-member has no provision for the brake line being routed that way I have 2 other 71 & 72 c10 1/2 tons set up without what I have described and you can see in these pictures. the member who sent me the pictures was sold the frame as a 72 did not specify weight class. Last is a picture of my Panhard bar c-member ( the one at the bottom)riddled with deep scaling rust reason why i want to buy something cleaner than what I have here but clean and correct. Can anyone shed some light on this for both me and the other member I'm dealing with. I am 99.9 percent sure the frame i purchased is of 72 vintage had a INL6 in it manual steering sway bar the last pic I posted