In answer to "where is it located" on a 1954 truck.
On 1954 trucks that have manual transmissions, the strap in bolted onto the top of the frame rail straight across to the hex-head screw/bolt on clutch housing (
three photos from Jim Carter). (JCs reproduction cable is 12" long and might/might-not be 2 gauge?).
I'll have to check to see where the strap attaches to a Hydra-Matic transmission.
Jim Carter sells a
repo clip for over the strap at the clutch housing.