Well, I seem to be done..!!
Bled the system as much as I could, although it doesn't seem like I put 16 litres in...
Went for a drive, and I am over the moon..!!
No leaks - coolant or fuel - and the carb seems to run well too ( but I have only the old Solex in comparison, and have no idea how good or poor that was in respect to how it should be. )
Either way, it is far more responsive, better pull under acceleration, and doesn't pull back any where as much as the old set-up did when coming off the throttle.
Feels like a different van now and makes the long hard slog worth-while.
I need to make sure I keep an eye on the coolant levels over the next few days I think.
I am sceptical about all of the air being out the system, but it doesn't get too hot and the fan is kicking in as it should too.
Once I have it running with no issues for a month or so, I will decide what to do about the choke problem ( I think. )
So anyone else thinking about doing this will need to factor in (over and above the carb and inlet manifold), the coolant system, different wiring configuration, throttle cable and any issues you may come across while doing those. Once I started I just kept finding more problems with the existing set-up. ( Maybe I just don't know when to stop

)
I want to pass on my thanks to everyone who had input in this - you all made this bearable and possible.
2 questions:
1 - What is an old Solex worth, keeping in mind I would only want to sell it as an example that needs refurbing?
2 - Part of the air filter is missing ( the bit that goes from the filer to the bottom right corner of the engine bay. ) Is that much of an issue?
( I don't want to be sucking crud into the carb now I have come this far..!! )
I will post a pic of the offending part if needed.
First I am going back out for a spin
