Champion radiator - I cut her open

I would run that 7-blader from post 25, in direct drive, with a hi-flow pump and matching 195 stat, and 100% water, with a low-pressure cap. Then a 26" rad like described earlier. This will provide max-cooling. Then get your engine sorted; Probably a little more initial timing, and lean out the low-speed circuit.Get it tuned for the new minimum coolant temp.
And I can't stress enough,fresh cold air into the carb. If she's sucking hot underhood air,when stopped,and at idle, that's just an endless cycle of increasing heat generation;like a runaway breakdown in a nuclear reactor. And moving slow in traffic is very little better.
After you have a rock-solid system, THEN, you can start dicking around with a thermostatic fan-clutch, and %-antifreeze, and number of fan blades, etc, each of which is likely to decrease cooling system efficiency. You can experiment with the decreasing efficiency until it is no longer efficient enough, and then go back to the last known good-working combo.
Don't forget; the thermostat sets the minimum working temp, and the rest sets the maximum. If ,in Adelaide, it is possible to successfully run it at 7psi, then your hoses and such will thank you for it. I see no advantage to run more pressure than that on a system than never reaches the boiling point. I understand that in your location, a higher pressure can provide a little extra protection on a marginal system.
And within reason, the hotter you can successfully run her,the more power she is likely to make; if you tune for it.

The advantage to running a Thermostatic clutch, is that it can automatically control that maximum running temp.And it does it without electrical controls. I found a very nice reliable clutch that maintains my system at 205*F. It's off an early 2000 Ford pick-up truck; an F-150 IIRC. It's been on there since about 2002/3. and that is over 60,000 miles I'm guessing. I highly recommend that one. It fit right on the Mopar 7-blade A/C fan, and was the perfect depth to center it in the shroud. Forget about power-loss with a clutched 7-blader.On the run to redline the fan will lag behind very significantly, as the fluid slips. Then as soon as the rpm stabilizes, and if the air-temp thru the rad has exceeded the clutch elements set-point, then the fan will lock up and go to work. With in a few seconds the air-temp will fall and the element will relax and the fan will go back to slipping. It will continue to cycle like this until the clutch element finds a happy place. The happy place varies with ambient temp, air-speed thru the rad and engine loading, and it's all automatic.
After the warm-up period, my system runs rock-solid at 205, under any and all conditions; which brings true peace of mind. I never look at that gauge anymore, except, I make it a practice to do so after every run to redline,lol, in case the belt were to flip off. So far it never has, since it first hit the road in 1999.
Sad to say I almost never look at that gauge anymore.I may have become too complacent,I know. It could happen to you,too,lol.
It occurred to me that you might want to know what I'm running;
It's a 367, 68 Barracuda with a manual trans and 3.55s. It goes 93 in the 1/8 at 3467#, which the Wallace calculator thinks is 433hp. (Well goes is maybe misleading; it went 93 one time, the only successful run of 4 that I made that day, that one and only time I ever tracked it. I didn't believe it either, so I immediately went to the timer window and inquired, and they verified that it was accurate. So then I went to visit the guy I ran against to get his opinion, and he verified that his time was accurate. So I did my due-diligence and retired the car for the day.Then went to the bleachers with my son and enjoyed our time together. He was 20 that fall.) IDK or care,it's never been dyno'd. And I'm confident it could idle indefinitely on the hottest days of summer, which here in Manitoba, rarely exceed 99degrees.lol. And it nicely survives multiple runs to redline and crawling along in traffic. With my starter gear,10.97, it will idle down to 4mph @550rpm, on flat level ground,heehee, so parades are possible.
It runs a 26" Factory A/C rad circa 1973.
Going back to the hi-flow pump, mine is a Milodon. It appears to very similar to the factory-type 8-vane pump to which they have attached an anti-cavitation plate. This is nothing more than an appropriately sized,thin,round,sheet-metal plate. You could fab up something down there and plug-braze it on for super cheap.The plate seems to increase circulation by shrouding the water in between the vanes, to prevent it from slipping off. It really helped my system and I highly recommend the plate. The Milodon has been on there since about 2000/2001, and has accumulated over 100,000miles, so,.all-in-all, even tho it was quite pricey, it was/is a good investment.No factory non-plated pump was doing the job for me.
Long story again, I know: novella # five thousand and four hundred and thirty-two