book doesn’t show any of the known 1957 Super D exclusively components. Like –
for instance and among others – Generator Bracket, Shaft to Carburetor Rod and
Coil Mounting Bracket.
listing a Super D cam doesn’t mean there wasn’t one. But like I explained
earlier: the ‘basic’ D500 was capable enough to handle the increased air/fuel
mixture flow at higher revs. And the higher revs were simply and solely
accomplished by adjusting the transmission rod to a higher shifting point.
Higher revs need more air/fuel mixture, that’s when the second (front)
carburetor comes in. In contrary to the 1956, the 1957 Super D dual carburetor
setup was progressively linked.