It seems that Federal Mogul makes V8 valves. This is an excerpt from there catalog pages, note they have the year span correct but the total number of valves wrong in the heading but the qty correct when ordering.
N ENG CODE - YAMAHA ENG - SHO - 24 VALVE
CHROME PLATED STEM
HEAD DIA-1.26 LENGTH-3.67 V4577 96-99 16
HEAD DIA-1.06 LENGTH-3.66 V4578X 96-99 16
This has not been verified, I am speculating that they are V8 valves but there are some inconsistencies in the catalog pages. FYI