OK the race was conic , the rollers Not .. not a good language engineer .. obviously ..

edit, above ..

the one Stronglight headset where the cone apex faces each other may be better ..

My Ice beater bike got that one .. delta & A9 the apex both face upward .
roadie and cross-tourer got that one ..

Id just build around Chris King's head sets .. Is my suggestion

have a 1" 2 nut, and a 9/8" Grip Nut...

my only threadless fork bike has an integrated Dia Compe/Cane Creek setup.
It came like that, frame machining holds the bearing cartridge.

IF You want those motorcycle bearings , buy them
and then engineer machining of the frame around them ,
rather than the other way around..