Where are you located at? I'm not there yet but I'm swapping a Cherokee 8.25 into my 82. At that point I'd be willing to part with an axle shaft (or two.) I'm in Wisconsin, an axle may be a bit fun to ship though. I also don't know if an SX4 axle would fit a wagon, I'd presume so but not sure.
If you want to know your ratio that's pretty simple. Jack a wheel up, chock the front, toss it in neutral. Put a line on the drive shaft yoke, turn the wheel a full rotation and count the turns and double that number. It'll get you close enough to determine the ratio.