There are adapters to run a mechanical spedometer with an electric piuckup, essentialy a variable speed motor. At least I thought I remembered reading about them on this site a year or two ago.

Or you could change your spedometer for a newer electric one, Stewert Warner makes some nice older looking ones.

There is a way to have both the brake and the spedometer.

Grigg

•1951 GMC 250 in the Project Journals
•1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
•1952 Chevrolet 3800 pickup
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"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-