Stupid shower thought: double shocks?

NASCAR stock cars used dual shocks well into the 70s. I can only assume because shock technology was rudimentary at best back then.

In reply to Appleseed :

Aw heck, a few Group B cars did too.

So did the final generation Mazda Cosmo, the one with either a twin turbo 13B or a twin turbo 20B.

In reply to MadScientistMatt :

Mustang SVOs had quad rear shocks, two for the usual jounce/rebound (up & down) and two to dampen lateral movements of the live axle

The only real Challenge related question would be, are two cheap shocks better than one better shock?  

In reply to Noddaz :

Probably only for heat capacity, and until there's a GRM Minty-Flavored 400 that won't be an issue...the effort of building and selecting a twin-shock setup has to compete with the effort of transplanting a "stiffer" shock from a heavier car that can be had from the junkyard with less in-budget parts on the car.

You could also probably mis-spec a shock. Ie a Monroe shock for an application with a really strong spring (like rear shocks on trucks and vans) probably has more damping than an oe shock for a light spring application.

Suspension stuff is super interesting to me (my side gig is motorcycle suspension valving), so I'm sure I'm going to end up writing too much. 

dual shocks in the bump direction are typically used only for a few reasons - unique damping curve shaping and avoiding mechanical limits. They were more common in years past, especially on heavy duty on and off road applications, for a few reasons: 

• fluid limitations. Modern shock fluid pretty amazing stuff, with very stable viscosity vs temperature, high shear stability for being repeatedly passed through valving and orifices, and good anti-foaming properties. I'm not really sure when the major strides were made, but in general from my motorcycle experience I'd say it was around 40 years ago when the industry really started to make improvements here instead of using basically ATF or hydraulic oil. 
• Cavitation. Most older shocks were not gas pressurized, so there was a pretty distinct limit to how stiff the damping could be before you would cavitate the shock, particularly on the rebound stroke. Modern shocks, both twin and monotube shocks, are generally pressurized, though there are still differences between "high pressure" and "low pressure" gas shocks. Head valves, as found on many remote reservoir shocks, can help with this as well, but this is unusual outside of off road specific or higher end race shocks. Older (and modern cheaper) shocks also often don't have any kind of membrane between the gas charge and the oil. today's quality shocks use an internal floating piston or bladder to prevent nitrogen from becoming entrained in the shock oil. Deaerated oil dramatically improves damping consistency. Before this stuff was available, running multiple shocks with softer damping would get you away from cavitation risk somewhat, and would keep temperatures in check. I monitor shock temperatures in some of my testing on bikes and have seen north of 300F, and even automotive shocks can get toasty with aggressive use. 
• Damping curves. You can valve a shock to do a lot of things, but it can be hard to do things like have digressive initial valving that becomes progressive, but not too progressive, at very high shaft speeds. Valving two shocks differently can help with this, where one shock primarily does your low speed damping but blows off at high speed, and the second shock may only come into play at very high shaft speeds, or maybe has very little compression impact but has significant rebound control. This is pretty common in off road stuff where you have a shock that's carrying the main spring, and then one or two additional shocks that don't carry a spring but are spreading the thermal load. Often one shock is conventional and the second is some form of bypass shock.

Most production automotive shocks don't have a lot of high speed compression damping, and have a lot of rebound damping. Depends on the application, but this is especially true for leaf sprung vehicles where the leaves add significant friction damping. I would think you'd need to be adding a lot of spring rate before you got to a point where the suspension wouldn't pack down with mix-and-match dual shocks, unless you found some really soft ones. The second shock should have a much lower motion ratio than the main shock so you don't run the risk of being massively overdamped. Or have multiple mount locations so you can play with the motion ratio to get it where you want. 

I've had some luck finding shock combinations looking at valving ratings from different major shock manufacturers by application (bilstein and others list a very basic valve stiffness or normalized number in their spec sheets) and then buying the cheaper branded shocks for the same application assuming they are similar. 

Depending on how crazy you're getting with fabrication and what vehicle it is, you can get motorcycle, ATV, and snowmobile shocks relatively cheap on ebay. I've had good luck in the past buying some Fox shocks off of the front of old snowmobiles and then revalving them to work in weird applications. It's easy to decrease travel or length as needed, and I had one set of Fox Podiums where I was able to mix and match parts on the cheap to add travel because the various different models share a lot of basic parts and dimensions. Shims are usually only a buck or two apiece, and rebuild parts aren't too spendy.

...yep, I wrote too much lol. Hopefully it's useful, and I'm curious what vehicle you're putting under the knife for this...

I had a '68 Bronco that came with dual front shocks.  Removing two of them improved the ride quite noticeably.