what I was afraid of:
Sounds like the very old 'factory' 8-magnet wheel.
A third-party add-on (no longer available) had a 24-magnet wheel for better resolution.
I think the guy who made them may have died ...
...or maybe he just couldn't get the magnetic disc any more.
That's why a lot of us have made our own.
As for the feedhorn conversion . . .
Original Birdviews have a cast scalar, with mounting points built-in for the six support legs.
I believe the Chaparral converter kit has a stamped metal piece, which accepts the six legs.
It's got a giant hole in the middle to bolt the Chaparral scalar and feed to.
If anyone who had one of those conversions had actually described or photographed it, I wouldn't be guessing.
(hint) -