For those that are going to comment about, "a truck not being a truck," please refrain.
So, I've been seeing a bunch of late model Mustang IRS setups popping up. I know the Jag rear and the TBird setup was popular a few years ago. Those are getting hard to find now anyway.
By the numbers, a 2015 Mustang weighs 3500-3700 lbs. They have about a 53/47 weight distribution. Also, most of that is "sprung" weight vs. solid axle vehicles having more "unsprung" weight. With that being said, The Mustang unit seems to be durable enough to use in a truck if one so feels the need to throw something in the bed.
The Mustangs have 13" brakes, Torsen diffs, etc... They're similar to the Tbird units in design, with the exception of being 67" wide. I've been looking at the cradle assembly they use. It looks like it can be carefully narrowed without too much headache. Of course the CV shafts will need to narrowed also. The Mustang has a long and short side. So, in theory the short side may be able to be re-used, but the long one would need to be shortened. Dutchman Axles offers this service for $75.
Didn't realize the Lincoln/Cougar/T-Bird units were getting scarce. They are nice to use since they are the right width. Like the Lincoln the best for looks (aluminum center section) but all are simple to mount. The one thing we have to do is modify the upper control arm to get the correct camber when used in an AD truck. I think these are an easier swap than the Corvette or outboard disc brake Jaguar units but none are extremely hard. When combined with a coilover shock front ifs and a coil spring Lincoln rear (not air bag) one can dial them in for any ride or load.
I've looked into the Tbird setup. They are still availible, but not as easy to find as the late model Mustang. The Mustang units are similar, like I said earlier. There are adjustable upper control arms on the market, along with everything else under the sun. They have good gear ratios, from 3.15 to 4.10. Plus the all come with a Torsen diff.... Not a bad setup. If you look at the cradle assembly above, I think the center cross pieces can be sliced and narrowed without much difficulty. The truck frame may have to be C- notched for the upper control arm, but that has to be done on a Tbird setup too.
I've found several of the Mustang units for around $500-$600. I'd probably spend that much on new leaf springs, mounts, and U-bolts for swapping a solid axle 8.8 in. I know there will be a little (or a lot) more fab work involved, but it may be worth it in the long run. Just thinking...
Been looking in to an IRS some more. The 99-06 Lincoln LS setup looks to be a viable option. They are plentiful and cheap. They were also used on the last generation of Tbird and Jag S type. They are only 61" wide, so no narrowing needed there. The suspension layout is similar to the 2002-2005 Explorer. You can even use the Explorer rear strut and coil spring on it. They have a weird 8" rear diff that can have either a 3.31 or 3.58 gearset. They don't have a limited slip option. The Lincoln and Tbird had traction control, so I'm guessing that's why. Digging through the parts catalog, the internals of the 8" are virtually identical to the 7.5 and 8.8, I'm guessing a 28 spline limited slip can be added without too much fuss. They do have the 5x4.25 bolt pattern, but Mustang Cobra hubs can be pressed on or the hub assembly and rotor can be re-drilled.
