Am pretty sure you can adapt the entire 89-95 setup to the earlier 79-87 frames.

Crossmember and all with some work.

Nice to see it back running smoothly again, thanks to all that made it happen 

Well, I am declaring the "swap the 1-ton 6 lug wheels and larger brakes" a nonstarter after physically comparing the parts on the frame I bought for the rear swaybar and some intense research. At least onto pre-84 5 lug Sunraders like mine. If someone's actually done it, I'd very much like to hear how you did it. Starting from easiest to hardest: The simple hub swap won't work. To do this, you also have to have the calipers from the next inboard part - the steering knuckle. The 1-ton brake caliper's bolt spacing is not the same as the 5 lug knuckle, so it won't fit onto the 5 lug knuckle. And there is not enough room in the 5 lug caliper to handle the larger diameter brake rotor, so no avoiding that. Next in complication would be to bring the hub AND the knuckle. However, the knuckle attaches to the upper and lower suspension arms with the ball joints, which are completely different. Both ball joints face the same direction on the 5 lug, and on the 6 lug they face opposite each other. So no go there. Next would be to swap one of the 6 lug ball joints out of the lower suspension arm into my 5 lug. No go there either, as they attach in different bolt patterns. Next would be a complete swap of the entire top and bottom suspension arms. This may be possible, but those two angled rods that go forward from the knuckle and mount on the front of the frame (strut bars) mount differently. So, it would require fabrication on the mounts, which are fairly complex heavy stamped metal, but I'm not saying it is impossible. For now, I've given up on it and am stripping the suspension arms and the strut bar mounts from the frame I bought, before taking the rest to the junkyard. I suspect those who have done this had 84 and newer Sunraders, which may be a simple swap. I am going to try to swap the 6 lug's heavier front swaybar onto my 5 lug - looks close enough to work, which would be a nice win in itself. Hope this is helpful to others.