I don’t think those have been available for about 20 years.

The only place I’ve heard of them being used was on that magazine build Ken Lazzeri did that went into that orange superbee(Chapman??).

I also saw them listed on a very early Indy price sheet.

68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123
Dealer for Comp Cams/Indy Heads