OK.
I've been giving the scope issue some thought, as I have both a 58 with folding buttstock and an 858.
The 858 is out-of-the-box stock, and is a much nicer rifle to shoot at longer distances. I keep imagining some kind of mount that would allow mounting a scope with at least moderate magnification. Even a Ghost Ring style sight, or a set of peeps like a BRNO model 4 would be better than the stock sights. My eyes seem older than the rest of me some days.
The 58, on the other hand, gives me a bit more of a problem with accuracy at distances over 50 meters. As it's already black with the synthetic "rubberized" furniture, seems like a good candidate for a 1X red dot or holo-type sight.
I love these rifles, especially the 858, and I think that even moderately good optics would be a worthwhile addition. Maybe a Bushnell Elite 4200 6-24x50 for the 858, LOL.
Thanks for the info on the Zahal fore-ends. I may give that route a try on one of them, anyhow.