[Pete]

I have a brand new set of off shore made hollow lifters in the shop now for refacing. This customer does this routinely. They come TAPERED, NOT radiused. That means they are cone shaped. NOT spherical like a ball. He just does not trust the original surface finish.

And yes the early Isky lifters were spherical. He soon found that didn't work though. The later ones were tapered.
The spherical ones would trap no oil film because the contact area was too small. That also resulted in extremely high contact pressure.

Very early Ford lifters were flat. Later they ground them on a 96 inch radius which is close enough to tapered that they trapped a boundry layer of oil and worked ok.