I can't speak to the "China" lifters. Companies will provide the country of origin for most parts, if asked. A search for "SBC lifters made in usa" gives some good results:
Clay Smith Cams:
https://claysmithcams.com/chevrolet-...aulic-lifters/
Chevrolet Performance lifters:
https://www.summitracing.com/parts/n...1044?rrec=true
(These have a distinct line around the bottom, which I was taught years ago shows the "hardened" foot.)
Comp Cams:
https://www.amazon.com/Competition-C...000CISAAW?th=1
(Pictures also show the "hardened" foot.)
Phosphorous is the component in ZDDP that provides anti-wear characteristics. Most diesel oils in a 40 weight are not subject to the Zinc restrictions. Many racing oils also have higher levels of Extreme Pressure lubricant. STP has an additive that will provide significant ZDDP increases.
For my older vehicles with flat tappets, I have some favorite oils. One quart of Delvac 15W40 plus four quarts of 30wt Non-Detergent ends up in my '36 Plymouth and it's been working for years. The '57 gets Delo or Motorcraft 10W-30 diesel oil. Both engines were built long before the current arguments over lifter quality which may be part of the success.