I'd recommend getting the 507 wallbox. I honestly forget what was upgraded from the 506, but when I bought mine 10 years or so ago, I read that the 507 was a better wallbox than the 506. Also, do you have the 1769 stepper for it? You will need that for the wallboxes to function.
I do not have the stepper. I saw a 507 (made in 1976) for sale on eBay but I wasn't sure if it was compatible with the 460 (1975).
The guy that was selling it didn't seem to know much about it... he said he thought it wouldn't work because they all changed to "digital" that year. But the 470 (for which the 507 was the companion) looks the same internally to me--at least at a glance.
I had a 454 and I had a 506 and a 507 wallbox. Sadly, I never hooked them up, but they both were the correct ones for the machine. The internals looked almost identical between the 506 and the 507. Also, the 454 and 460 were pretty close machines, too. I just pulled up an online pic of the internals for a 460 and it looks exactly like my old 454.
Just keep in mind that you will need the stepper motor. You can't just buy a wallbox and hook it up without the stepper.