Speedwin angle plug bb heads

I picked up a bunch of Hi Performance Car magazines at a swap meet at a local fairground. These are more interesting and have better tech articles than the west coast magazines.
Anyway, has anybody ever got the slant plugging done? I don't recall ever seeing a set anywhere. Joe Jill, owner of Speedwin, was a tech consultant for the magazine.

IMG_4118.JPG

IMG_4119.JPG

IMG_4120.JPG