There are some possibilities to consider if you wish to try to get the TV working like a regular retail model, which seems to be your preference.
Firstly, you can get the 65" A board and it seems you have one on order. It may work - in the sense that the TV powers on a produces a picture with no warning messages - or it may not. It's possible, e.g., that the board will detect it is in the wrong TV and not work. On the other hand, it may be that there is very little actual difference between the boards for the 60" and 65" and the boards may be interchangeable. However, you should be cautious. Even if the TV does appear to operate correctly, the 60" and 65" models may have slightly different cell geometry which would necessitate the use of colour tracking tables specific to each of those particular sizes. Or there may be other differences. I don't think the 65" A board is likely to blow the 60" model up, but still I would be cautious about using the wrong board for that size.
Secondly, you can get the fans to work. For me this is by far the cheapest and most straightforward option. There is a sort of extension lead the fans connect to that goes to the A board. If you could obtain the correct one for the 60" model (it's only some wires and a connector), then that will suffice to connect the left and right fans. We know that regular ZTs in this size come with two fans so that is a configuration that I would hope would work. My only reservation would be that there might be something unusual about your ZT that means an extra fan is required. In which case, you could do the above and connect up the two fans and then find a way of connecting the 3rd. If you go this route then, to my mind, you will end up with the closest equivalent to a regular 60" ZT. Moreover, you won't have to replace the A board again, an operation that comes with a certain amount of risk.
You might wish to look at this thread
, where people are experimenting with fans on their VT60s.
Once again, if you could supply me with the service manual/technical guide mentioned in the thread above, I would be very grateful. I'm fascinated by how these things work and am always keen to extend my knowledge.
Good luck and do take care, especially with any ribbon connectors.
Picture modes for the US ZT60 from page 36 of the eHelp document here
THX Bright Room