To convert to discs or not convert? That is the question!

You can buy new "kits", which are just the factory 1973+ disk brake parts, ~$750 ebay. The kits the guru was talking about were likely after-market Wilwood, SSBC, etc. You can get parts for those now, but might be harder to find than factory parts in 20 years. Don't even consider the early K-H disks for your car, since not original.

One other thing to consider is wheels. I think all drum brake cars, even 1973+ had the early 5 x 4" pattern (SBP), whereas 1973+ disk cars were 5 x 4.5" (BBP). If your wheels are SBP and you want to keep them, that narrows the choice. Wilwood makes kits for both 9" & 10" drums. Before that, look at Scarebird's kits. Much cheaper and use Toyota and GM parts, which will be the easiest to find in 20 years.

As far as stopping ability. Well-maintained drum brakes will stop a car fine. Can't they skid the tires? Can brakes brake any more than that? You will only experience brake fade from continual braking (not enough time to cool) or one-time braking from very high speed (say >90 mph). The guy who claims his Cadillac shoes "faded" when braking during a turn had some other problem going on, unless he was taking the turn at 90 mph.