IMO I find it quite funny that people are all serious about people wanting to install a out of date harness in a rec vehicle that is nothing more then a glorified stock rig. Meaning what vehicle here can and will do over 50-60mph and in a situation where it will see more possible damage/forces, if crashed, then say a completely stock XJ on the 91 fwy doing 75MPH and someone clips em.
Stock 20yo webing on stock latching stock seat belts, dont come apart. So why should a rec vehicle that will never see that type of incident, but even if it did, that was deemed safe by the DOT with a 1.5-2" webing, be worried with say, 5yo 3" webing, that just has a fancy tag that is out of a 2 or 3yr window of racing safety?
Now if the webing is extreamly faded from sun exposure, or cut or frayed (no matter whether its stock or aftermarket 4/5 pt harnesses)then I wouldnt use it no matter what belt/harness...
There are a few reasons that people (like me) have such a problem running old out of date race harnesses.
One reason is the webbing on a stock DOT seat belt is a much tighter weave holds together much better and longer than than a race harness. Look at any race harness out there, the weave is much looser and wider. The reason for the wider weave is that race belts are made to stretch in a crash so that your body doesn't take the full impact of the crash. Stock DOT belts are weaved much tighter and more solid, because the ratcheting of the pre-tensioners (pre-air bag) or the gas charge tensioner (with air bags) works to slow your body down. Its not the crash that injures you, its the ubrupt stop at the end!
I'm a racer and I have been working at a race oriented shop for many years now and have seen first hand the effects of old harnesses. The biggest thing with old race harnesses is that they get stretched a little more each time you strap yourself into the seat, then they stretch while your racing and taking the G-forces of cornering, braking or in off-roading the jumps, bumps and hill decents. They do wear out.
There are so many companies out there making harnesses these days that for the $50-$75 dollars for some good budget friendly harnesses its not worth the risk to run some old worn out belts.
I don't however have a problem with new old stock out of date harnesses. Unless they have visual problems of course (sun fading, freyed edges, cuts, etc.). Those have not been stretched and worn, they are just out of the manufacturing date.
I am not trying to "preach" my way of thinking, but I do like to see every person make there own decisions with good information to learn from.
I hope that my points make sense and don't just sound like I'm trying to force my opinions or be a "know-it-all", I just don't want to hear another story of someone getting hurt or worse due to old used harnesses.