I thought about using a frame off of a Dakota, but I would rather put spring mounts on the subframe and run the car how it is. I feel it would be cheaper just to put mounts on the car since my uncle can custom make and weld the mounts for me.
It
might be cheaper, but you'll want to reinforce those mounts very well. And as 75slant6 said, I would use subframe connectors with that at the minimum. How well you reinforce the mounts and unibody will determine how long everything lasts. Not as much of a problem if you just want to cruise this thing on the street, but if you actually have any kind of serious off-road aspirations for it the unibody will need some reinforcement. In addition to the subframe connectors I'd be looking at some kind of reinforcement for the shock towers (whether you use them for shocks or not) to triangulate the front frame rails. The unibody is not designed to carry suspension loads like that directly on the frame rails, the spring forces from the torsion bars are carried by the K member and torsion bar crossmember not the rails.
You can see here the "J" bars I added to my car, running between the firewall and front end of the frame rails. I also added subframe connectors, torque boxes, and a radiator support brace to my car to stiffen it up for handling purposes.
The other issue that may come up is the transmission tunnel. Bolting the whole car down on a Dak frame raises the body and uses the truck mounts. Putting the hangers on the frame means that the transmission, transfer case, front driveshaft etc all have to clear the body too.
Doing this right, no matter which way you go, will take some time and effort. If you just slap some leaf spring hangers on the frame and redneck the thing together it won't even be safe, and who knows how things will work out for suspension geometry. Even assuming you end up with something that's tolerable, it's longevity would be an issue. You basically have to design an entire front suspension to do this right, although a leaf spring front suspension is pretty simple. But you still have to determine the length and arch of the springs, the angle of the springs, as well as the hangers and shackles, determine the shock length, keep the axle centered in the wheel well and maintain the wheel base, set the angles of the driveshafts, and then match the ride height front and back. And that doesn't even address what you're going to do for steering. The whole steering system will have to be redesigned, you'll probably have to come up with some kind of cross steer system to keep everything lined up. But with that much lift you can pretty much guarantee that the stock centerlink, idler and tie rods will be a disaster, and probably won't be anywhere near where they need to be for the to work with the front axle and spindles.
There's a lot of things to consider if you actually want something that's enjoyable to drive and relatively safe. After all of that, getting a Dak frame out of a wrecking yard and just sectioning it to the right wheelbase starts to look like the easier way to go. Everything is already in place, the suspension and steering all works, all you have to do is get the steering column from the Duster hooked up to the Dak's steering.
lol
