The DaviesCraig electric pumps have been used successfully on several Improved production cars in Vic and other states.
My only recomendation is to run a 20psi+ radiator cap to ensure good block presure and monitor this with a good guage or log it into the engine managment sys.

These pumps dont make any presure.

They are recommended to be placed on the bottom hose.

Rezlo can it be that freakin easy especially because there is an A12 lying at my parents house.

Normal town driving, does this combo still work, or does the thermo fan start doing overtime?

First things first, fix the plumbing then see if you still have a problem. No need to make a bunch of mods when there is something obviously wrong with your current setup. 2 quick ways to get the over flow tank connected correctly- Add a TEE fitting into the heater return hose or add a second heater return TEE into the lower radiator hose. The other obvious thing is the over flow tank needs to be higher than the radiator.

My fans never run more than 50% duty, and its been stupid hot here recently, zero problems

I wouldnt touch those DC electric pumps, seen two fail already for no reason costing the owner a motor each time.

As with everything datsun, keep it simple (my system is stock besides radiator and fans) and 95% of the time it will work just fine for even the most demanding situations

The early Davies craig water pumps were far from reliable. I haven`t seen a failure on the latest units.

Even so, I would be sticking with a mechanical pump where ever possable and use one with a cast impeller not the pressed metal type. There is some very good cast impeller designs that shift alot more water more efficienty and dont have the cavitaion problems at higher rpm.

I`ll post a pic of an "L" series unit with a better impeller.

Its a little off topic probably worth adding to the discussion.

On that note, I am running a regular $10au cheapy auto parts store water pump with pressed impeller.

Ive found during engine dyno testing of race engines that the pressed metal implellers dont make the block presure and are prone to cavitation.

On engines that are close to detonation with a cast impeller would detonate with with a pressed metal impeller. This is because the block presure dropped from 22psi down to 10psi (tested with non presurised cooling tower)

The incresed block presure prevents steam pockets forming around the combustion chambers.

I am refering to race engines tho, not hot street engines used for occational sprints.

sikyne, where do you get a 22 psi radiator cap?

Just an FYI, The Tomei TS as well as most of the A's running in full race conditions to this day still use stock pressed water pump just with a small amount of the ear's removed to slow the flow rate (as do most of the newer full race SR's, RB's etc)

I am not saying cast isnt better, it just isnt needed.

Arent all the original's cast impelers?