best to skip calling your truck an Apache here, which could be a 1/2T long or short, a 3/4T or a 1T [58-62], and use the year instead
aside from the fact that the assembly manual was printed in 55 so has nothing that's specific to an "Apache" of any year, that doesn't look like anything I've seen on a 58 1/2T, might be a brace a PO added somewhere? maybe you have a 3/4T or 1T with the driveshaft hand brake? maybe it was something found loose when you got the truck?
Bill
