In addition to the issues Patrick mentioned, Scout front axles were typically set with 0° caster. To make them work on a Jeep you need to grind the welds on the knuckles/axle tubes, rotate the knuckle to the required caster (commonly 6° +/- 1° ), and re-weld.
You'll also need to weld new spring buckets for coils or perches for leaves, depending on your plan.
Of course you'll have to match gearing to your current rig if you are only doing one axle... otherwise make sure gearing matches in both axles you install... and that gearing is a good match for your tire size.
Since these are 70's axles, probably best to do a master rebuild on the R&P in them, even if you keep the existing gears.
Also keep in mind that the front axle wheel bearings are not sealed like on a TJ, so they require maintenance frequently. Especially if you run in conditions that are dusty, muddy, or involve water.
Then there's the brake issues...
Sometimes Free Stuff isn't the best way to go...