Speedometer cable

I forget what that little box does exactly. Turns a light in the dash on when you go over 55mph? Anyway... you dont need it.
There are a couple different routes you could go. I would buy the more common one-piece cable for a different model a-body before spending on a 50+ year old cable. If you think the inside of your OEM sheathe is still good, universal cable cores are available. Good luck which ever route you take.