I have started assembly on the 7th engine I have used Schubeck flat lifters in and all I can say is that I am very happy with them.
The first engine has over 7000 miles now and hasen't even needed a valve adjustment. They work great on the street where low speed and idling reduce
oil flow over the splash feed lifters like those used in all early 427 side oilers and all center oilers. To take full advantage of the lifter design a custom cam with quick opening and closing ramps should be used. I have had cams made that approach solid roller cam specs and have run as much as 180 lbs valve spring seat pressure with no wear or durability problems.
I think they are great and in the long run well worth the investment.
--Mike