Lifter quality "food for thought"
There is no coating on FT lifters. If you some that are 25 yrs old, not rusty, they are good to use. Perhaps spray some WD-40 into them, then a few drops of light engine oil to make sure the inner piston moves freely.
You can convert hyd lifters to sol lifters by removing the bits underneath the inner piston [ a spring & valving ]. Replace with steel washers to get the correct height. You now have sol lifters.