Mike,
My understanding is that evolution of the F1 hydraulic pump took the following path:
Stage 1
Alfa Selespeed F1 pump Part no 51736315 (as mentioned in Loz's post), the equivalent of which would have had a Maserati/Ferrari number (I do not know what that is). I am convinced that this is the part that was originally fitted to my 2004 QP. I have replaced mine and have driven over 1000 miles on it.
Stage 2
Part number 213264 as recently supplied by Eurospares and Maranello. Now my understanding is that only the electric motor (nothing else) was upgraded with this part and the pump head remain identical. Indeed the US guys video at he top of this thread is implying just that. What he is saying is that you can use the electric motor replacement (that he supplies) to change your stage 1 hydraulic F1 pump into a stage 2 (i.e. part number 213264 equivalent). I would have tried this had I not got the Alfa Selespeed part to work. As the American says, the replacement electric motor (produced by Magneti Marelli) costs 'less than half' of the price of the complete F1 pump.
Stage 3
Part number 247223 as currently supplied by Eurospares (see link in my previous post) and Maranello. It is my understanding, and again please correct me someone if you know different, that the electric motor has been upgraded again to make it more robust.
Loz, perhaps you could also comment? The only reason I posted was that someone on the forum had commented on this US guy's youtube video and I was trying to add more meat to the bone as it were.
Now my own advice would be to use the latest part if you can get it for a price you are comfortable with. However, if you would rather save some money and use the same F1 pump as your car rolled out of the Maserati factory with (stage 1) or the next evolution of it (stage 2 - part number 213264 or equivalent), then why not? It will work but I guess what Ferrari/Maserati are saying is that it won't last as long as the latest evolution (stage 3 - 247223). In my case the original stage 1 lasted 40k miles - if it manages another 30-40k I'll be happy with that!
Cheers, Dhanj