Yeah, the only place for a swap would be your local wrecking yard but beware grease worms you want to be sure to buy a guarantee with an item such as that! You don't know just how the previous owner was coming to driveability they could have been a hard accelerator spinning tire alot and all! If anything you can probably persuade them to pull the backing plate to inspect it for metal flakes resulting from abuse? Or shop around for a private seller parting out a dakota of your truck identically So the gearing will be the same! Hope you find what you need?
There is no currently available solid axle swap kit. Adding a solid axle to a truck that never came with one, is a custom job.
A solid axle swap is a really big job and not for the faint of heart. If you plan to tackle this yourself, I would highly suggest you do your homework, develop a plan, and get real acquainted with solid axle swaps in general, before you turn a wrench. Keep in mind that welding will be required. If you have welding skills this can be a rewarding effort. But if you don't have skills or your skills are currently weak, don't risk your life because one bad weld can result in a catastrophic failure that could kill or severely injure. Get really good with your welding skills if you need to.
Your next option is to hire a mechanic/fabricator who can do the job, but keep in mind that it can get real pricey very quickly.
Which axle should you get? It depends. There is a lot to consider before you settle on which axle you should get. What kind of off roading do you plan to do with the truck? What kind of suspension system do you want? How much engine are you going with? Are you planning to use the current transmission? Do you have a current transfer case? How large a tire do you want to run? How custom do you want to go? You may also need to swap the rear axle.
In my case I selected a Dana 60 front axle out of a 98 Ram 3500, which was fully rebuilt with heavy duty internals to survive a Cummins turbo diesel and 41.5 inch Pitbull Rockers. That axle was hung to the frame using the Ram's original coil springs with custom radius arms in place of the original 4 link. I also swapped the rear axle too. I went with a Dana 70.
There are a dozen different ways and many different axles that could be used, but start with answering these questions, then once you have an idea, make a plan and pick those parts that best fit your plan. Don't forget to keep it all within your budget