Best product for treating old vinyl

I have a vinyl interior and vinyl roof on my 47 year old Duster. I religiously used a product called Rally Vinyl Top Dressing by DuPont back in the 70's. Sadly you can't find it anymore. That stuff was the BEST, that's why my top and dash pad have lasted this long. I'm just worried that the sun will take its toll on both unless I can treat it properly. I want to preserve the surfaces with the right product to keep them soft.

Does anyone know of any current products that perform as good as the DuPont's product? I don't want to apply the current products that might destroy what DuPont Rally Vinyl Top Dressing was able to save for such a long period of time. Any thoughts or insight?

Thanks, Jack