Well you are in way over my head... But Im still going to add a few things.

1. Look up member Crazy4x4rt. He put a SAS under his dakota. Best I remember he used a jeep wagoneer front end.
2. I would think anything out of a full sized truck would be too wide and would require narrowing. That alone will blow your $1,000.00 budget.
3. Strongly consider getting a beater vehicle to drive while you attempt this swap. These 1 month projects have a way of turning into X years projects....
4. Assuming you can find a front axle and spring set up that would basically drop in and weld shackles to the frame, you will still need some custom steering parts, and a custom driveshaft.... Not to mention wheels and tires after its all done.
I would think your budget needs to be several thousand to complete this project.

If you do go with this swap, take pictures and keep us up to date on the project!!

 

It isn't going to matter if the axles are already on a vehicle with leafs. Chances are they are going to be the wrong distance apart anyway. Sure you can build your frame brackets to accommodate it, but you still will have to set the truck down on it's own weight, make sure the ride height is correct, then set your pinion angle. That means you will have to weld on your own leaf spring perches to the axles anyway. 1500 axles will work just fine after you cut off all the brackets. Full sized axles are only around 6" wider than what's under there, so you can use wheels with a deeper dish and end up with the same over all foot print. Most of the newer Dodges have a much deeper wheel dish. If you use a couple 1500 axles from around the 90's, they will probably be a few inches narrower than the new trucks. I'm sure this info can be found somewhere online. No matter what, this is custom fab work and unless you know exactly what you're doing, this will not be a daily driver right away. Once you get the ride height right, the pinion angles set, you still have to articulate it and set your bump stops, then weld up shock mounts, you'll want a drop down pitman arm if you lift it. I suppose if you try to keep it stock height then a lot of that stuff will work out better right off, especially with the rear axle, then you could lift it and make clearance for tires later. Hopefully your Dakot has the same gear ratio as one of the 1500 Dodges. I know 3:55 gears were very common in both. Don't get discouraged, just plan plan and take lot's of measurements. Premake as many parts and brackets as you can.