<VV> Lower choke control rods size?

[Grant Young]

Checking to learn the differences and applications for the lower choke control rods for our HV carbs. Apparently there is a short (6"?) and a long (8"?) style. Wondering which ones go with which year engines? I know this won't be as much fun as talking about oil and grease, but have a newbie contact who says he has some rods that are too short.
Thanks,
Grant