For the pinion seal on the steering gearbox, I measured 1.375" on the shaft and 1.750" on the housing. This cross references to SKF Seal number 13509.
That crossmember looks like it has a doubler on the bottom that's riveted on (rivet where the crack is.) I would line up the crack and weld it, then weld a fishplate on, possibly a couple of pieces of angle iron over the top and welded longitudinally.
You are correct, it has doublers on both sides. I like that reinforcing plan - I'll get the box pulled off, and hopefully by then I'll have the truck able to move so I have an easier job getting the welding leads to it.
