Out of all the square bodies I've owned,only the '79 C-10 Bonanza 2wd I had was the only one that cracked the frame at the steering box..
Had a certified welder stitch it back together,he felt it wasn't a must to plate over it,so I took his word for it..it never gave any grief again..
Most of the 4x4's I've had ,were equipped with Fisher plows and the plow push frame evidently beefed up the frame enough not to let it flex and crack there..the 3 K5's I had,a '71,'72,4x4,and a '71 K-10 Suburban and a '75 2wd K5,all had no frame cracks,none of them had ever had lift kits or big tires,or plows on them..
One truck I had,a '77 GMC K2500,had been hacked by a previous owner with ill fitting lift kit front springs and 36" tires when I first got it..removed all that crap and put it back on stock springs & tires--the steering box area on the frame never cracked,but the cross members had several sheared rivets and had been welded to the frame,and bolts put in place of the rivets..that truck got a Fisher plow setup as soon as I got it back on stock suspension..