The story I've heard is that each Ford tractor dealer was required to take one gold demo. It could be any model the dealer desired. If that's the case, there were about 2600 - 2900 Ford tractor dealers at that time, so it stands to reason that's how many gold demonstrators were built.
I'm no expert, I just repeat what I've heard or read on the subject. I was only 3 years old in Jan 1959!