It's different between 48-50 and 51-52, not sure about 53-56 and beyond. On 51-52 it goes thru a hole in the firewall right near center of the firewall, loops down and goes along the trans to the rear. It shares the hole in the firewall with the choke cable and throttle cable. Just keep it away from electrical stuff in the engine compartment (my cable has a bare steel sheath, some are plastic coated).

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