My dad and I have been looking at a bunch of different shafts to see if anything is a true bolt on.
Unfortunately, it doesn't look like any of the shafts out there (that I've seen) will work as is. Well, work as intended by the manufacturer.
The steering box end seems to be almost universal between years and jeep/GM. The steering column end is different as most thinking about this know, the bolt through the column, or the bolt that clamps the shaft to the column end.
I'm not a huge stickler of safety, but the steering column end (at least the later bolt through design, which is hollow) is pretty flimsy metal as is. Grinding off of that to *me* (and my dad) doesn't appear to be a good idea. May work a long time, but if/when it does give, you could kill somebody besides yourself, which is where I personally draw the safety line.
The jeep style ones are similar, BUT the way the shaft is "keyed" is different than the GM shaft. If you look closely, the "flats" on column and shaft are not even on both sides. The GM truck bolt through column end has "even" flats on both sides.
The Astro shafts are also not "bolt ons" but I can't recall why right now. I do remember that it's because of the mismatch in column ends between them and our trucks. Full size vans that we've looked at are also not "right".