Not sure what you need to hear to feel safe about your purchase. Usage and mileage certainly are factors and if your car is not a daily driver and you live in an area where roads are decently maintained, you may never have any issues.

If its any consolation, there are strut suspensions out that that do not have the magic 16" load spread on the control arms and they manage to absorb a fair amount of abuse along with daily usage. While they can and do occasionally fail, it certainly has some mitigating factors, such as maintanence, and is typically not a major newsworthy item. Is that to say the AlterK is all that, I dont' know. I've never used one. But it isn't a huge bane to reliability either.

IMO, a lot of the benefit of these aftermarket suspensions comes in a few key areas; reduced weight, improved precision, greater adjustability and match spring/shock rates to the application.

To address these; you can reduce weight in the nose of the car in more economical ways than replacing the entire suspension. Fiberglass cost about $10 a pound to loose weight with. An Alterk costs you around $50 a pound.

Improved precision is often times comparing used original or partially rebuilt systems to an entirely brand new conversion. I would epxect all new everything to have better precision than original. Will a R&P maintain that precision for longer than a recirculating ball gear box, probably. But I also doubt most of these cars are accumulating that many miles any more to make a fair comparison a decade later.

Greater adjustability is a benefit that is not as easily obtained with stock parts. The factory mopar design does have limitations, but can usually show sizeable improvements with a few key pieces being changed out. If you drive in an environment that necessitates rapid changes to spring and shock rates or slight variations in geometric changes, then the aftermarket set ups do have a considerable advantage. However, this tends to be highly contested competitive environments where a lot of this vintage of mopar do not play.

Finally is the matching of spring/shock rates to the application. This is, IMO, the biggest benefit of these systems as you have the designers or technical staff designating what peices play well together. Contrast this to your average street enthusiast who tends to buy the biggest this and the cheapest that and munges them all together and then its easy to see why things don't perform well and along the way the car has lost a fair amount of reliability and comfort as well as performance. If you can understand how all the peices work together and where to compromise and where to splurge to get the matched set up to ahcieve the proper rates sets and percentages, it is entirely possible for a 40 year old design to match a modern design in performance and comfort. But, not everyone can pull that rabbit out of the hat and if thats the case, you may be better served by having someone else figure it all out for you.