My point was, you MUST have a cam ground with a lobe that takes advantage of the larger diameter lifter foot. You can certainly put them on any solid lifter cam and they'll work JUST LIKE A REGULAR flat tappet.

My other point was, as cam grinders haven't been feeding the mushroom lifter need for several decades, all mushroom lifter grinds are apt to be behind the times.

A third point is, mushroom lifters were a crutch for racing classes that didn't allow roller lifters. If the classes had allowed rollers, the mushrooms would have been gone in a heartbeat.

R.