Nick - Least expensive (not considering shipping costs) I found for a suitable new speedo cable is this Generic 1939-72 replacement unit from Classic.

The only Tech Tip I can currently quickly see if this Art Deco Speedometer Rebuild Legacy tech Tip, but I don't think that answers your question.

Hopefully another Bolter will chime in with what they've done on their truck. wink

~ Dan
1951 Chevy 3 window 3100
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"My Grandpa Carl's Truck and How it Became Mine"
1966 Chevelle (Wife's Hot Rod) | 2013 Chevy Silverado (Current daily driver)
US Army MSG Retired (1977-1998) | Com Fac Maint Lead Tech Retired (1998-2021)