Hi,
GM has been using beehives on stock production motors since the early 90s. The lowly 3.1 v6 got them in about 93. Buick followed suit on 3.3L and 3.8L V6s soon after. They make sense, less retainer weight to control, and a variable spring rate,I believe.They work great with roller cams, which I think is the reason the engineers like them.This is my understanding, anyway.