Steering components swap/update combination for '70 C10: PS and tilt conversion

[Farm Shop]

I'm currently in the process of swapping the I6/PG in my 2wd '70 C10 for for a 1999 vortec 454/80e, and want to convert it to power steering at the same time. I plan use the serpentine '99 PS pump/lines, and it makes sense to source a steering box that won't require the expensive metric-to-standard adapter fittings, which brings me to my first question:

- What year did square body trucks start using metric o-ring PS line steering boxes? Looks like I need a '79+ with the 1970 pitman, but just want to be sure.

The newer box then brings up a new issue of the metric rag joint not working on my 1970 column. Sure, a $50 Dorman replacement rag could get me by, but this seems like a good excuse to swap in a tilt column with a rag joint that bolts up to the '79+ rag joint. This is where I have a hard time finding good solid examples.

- What is my best option for a tilt steering column that is easily found in a junkyard? None of the local yard have old iron in them any more, so the 70s-80s vans, and OE 89-72 tilt columns aren't an option. I'm pretty much stuck with C/K model trucks (88-94 work?), or square body trucks if I get lucky on CL. I'm not worried about key location, and opening up the dash bezel for the larger shaft diameter can be worked around.

Thanks in advance for any help, and pictures would be very much appreciated!

Here's my truck I'm working on: