More Teeth on the Speedo Gear Will Make Speedometer Read Lower, Right?

WV64Signet said
And something that I'm not clear on, and sorry for taking the discussion in a little bit of a tangent, The chart above and an online calculation tool that I have used both (for me) came up with a 41 tooth pinion... But if I go into the tech manuals and look at a comparable tire (14") the solution set was either a 19 or 21 tooth gear. Seemed like a pretty big jump to go from 17 tooth to 41 tooth when I'm only off about 10 MPH.

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I think you're mixing apples and oranges- the Brewer's chart posted above is for '66 and newer transmissions, your FSM chart appears to be for '65 and earlier. They're two different animals.
Here's the full page from Brewer's: