back in the 80's i had a truck repair shop make me up a cable for a stewart warner tach to a prestolite[?] duel point distributor from a 60 300F. the cable didn't last very long, so another was made as a replacement at no charge because it didn't last. same thing happened. there were no sharp bends or kinks in the housing, so just to avoid the headache, tach was replaced with an electric one. later, it was brought to my attention the probable cause was likely the core material for a speedometer is wound backward from that used in a tach application. as it was such a long time frame past, the cables [ the original is still around somewhere, but the 2 longer replacement cables that broke are gone] are nowhere i can compare to see if this is a true statement. this maybe something to check into before getting one made up. can anyone confirm this as fact or fiction ?