I suggest that if you put a vacuum guage on the manifold of the engine that has two Weber/Solex/DelOrto carbs, & has a cam to justify them, you will find it has no vacuum to speak of anyway, so the disributor should have already been set up for this engine without a vacuum advance canister fitted & the vacuum advance plate locked down.
This is why the triple Weber equiped Bathurst Chargers had no vacuum boosters for the brakes, .... no bleedin' vacuum.

But for basically stock engines that DO develop good vacuum at cruise, the retention of the vacuum advance feature is a bonus.

Generally speaking, the coolant bypass port in a Datsun engine is too small to cause overheating by virtue of it causing the coolant to circulate only within the engine itself.
That business about coolant traveling too quickly through the radiator to shed it's heat is just an urban myth. If it is too quick to shed heat, it's too quick to pick up heat from the engine too.
With the thermostat wide open the radiator does its best work & that's a practically unrestricted flow.

The removal of the thermostat from an otherwise serviceable cooling system will usually result in overcooling. [big time]

and without a thermostat the car will most likely overheat due to the water travelling to quick through the radiator and not having time to cool....not that its relivant

what would one do in regards to running twin 40mm dellortos where there is no vaccum port, apart from disconnect it and just advance the timing

Vacuum advance units are a bit like thermostats. Your car will run without it, it will run for years without it, but it will not run at it's BEST without it.
Thermostats & Vacuum advance units cost the manufacturer money to make & install, and our cars were competing in the low cost end of the market where every dollar counted, yet the manufacturer still put them in.
They did it for a reason, a very good reason.

When you are operating at light throttle & at cruise speeds, the manifold vacuum is high, so the vacuum advance kicks in & allows the meager amount of fuel that is being admitted to the cylinders to be ignited at the right time & to provide the best power result at this throttle setting.

If the vacuum advance is not kicked in, then the engine's ignition timing is effectively running retarded from the optimum position, requiring more throttle opening to maintain the desired cruise power setting.

End result, ... increased fuel consumption at cruise power settings, so I suggest that you make the effort to find a serviceable unit that is correct for your car & maintain your pocket rocket properly.

Its no drama. They are useful . They improve performance as revs rise and the carby increases air flow. Blah blah blah.
You dont need it

my vacum advance is buggered and i was wondering if i can do with out it.