The stock ones come from Areostar vans. You have to take them to the clutch shop to be shortened. My clutch shop will make one up for 100 bux. Includes all cutting, welding, and balancing.
We have one in Tammy's car for a 79-93 mustang. We also have an 8.8 axle so no moding was required. I set up a t-5 in my buddy's 73 maverick and he bought the same drive shaft. I just have to replace the rear U joint with one of those adapter u joints 3120-3110 I beleave, So it would fit the smaller 8" yok. They had them at auto zone I don't remenber the part number.
I got a used one at a swap meet for a Mustang for $50 and took it in and had it shortened. I think it cost me $125 with the rear joint.
They have some give to them, unlike a steel driveshaft. Sometimes that give can have an advantage when you use a manual transmission. Of course you can twist it up unlike a steel one. But the pretty factor and the lightness is what attracted me to it.
THE benefit is being lighter. We talk alot about 'parasitic losses' in the drivetrain... Like the C4 eats up less HP than a C6, for example. Same thing. An aluminum shaft eats less HP than a steel shaft. More power to the wheels. Also, any weight that spins lost, is weight loss far more beneficial than static weight loss. For example, lighter rims are more beneficial pound for pound lost, than say fiberglass fenders. Both are good, but rotating mass has enertia and parasitic loss. The biggest drawback is that aluminum, while strong, tends to 'work harden'. Meaning it eventually becomes brittle after being stressed over and over. That said, I have seen plenty of steel shafts break and even seen them twizzle up like silly straws! (BBC power!)
I used a aluminum mustang one same years as you mentioned. c4 and a 8 inch. It was a tad short but worked with no issues. The u joint you will need if you keep the 8 inch or small 9 inch small pinion yoke is a Part#331 or 347 brand= Precession( I cant remember at the moment other than it was a stroker kit number) With a nine inch you can get a long pinion snout to make up for the length. I don't recall seeing a long pinion snout for an 8 inch. If you have the larger snout on the 9 inch the ujoint on the shaft will drop right in. Like I said my car was far from stock and I had no issues even though it was a tad short.
I don't think the aluminum shaft will twist up. It will just fatigue and crack. I have seen steel shafts that do this. Once upon a time they used to drill a hole for a zerk fitting and fill the old steel shafts op with grease to cure the twist and absorb vibrations. Kinda like a fluid dampner balancer.
http://www.actionmachineinc.com/driveshaftrepair.htm nice info here and an aluminum shaft would appear to have more give. Though I have never seen an aluminum shaft twist up like a steel one
Carbon fiber shafts are the $h!t... They are high dollar though. I have never seen one for a Mav, but they sell them outright for LS1 F-bodys. Almost 800 bux!
What do I need to say for our more 'senior' members? Boss or maybe Groovy? How about Keen or Swell? That's just swell Beaver!