It now sits on 20psi at idle with the oil temp around 70 degrees. It will drop lower when the oil is >100.
I was finding that at idle when it was very hot, the gauge would barely register above zero. When revved, it would be between 25 and 30 psi. When cold, it is now 50 at idle. From what I have read on the Interwebs, what I have now is what is expected.
I changed the bearings the last time that I had the engine apart, though there was no unexpected wear on the old ones. It's possible that the gauge is seeing less pressure than the bearings, considering that the gauge is at the furthest point away from the oil pump.
I use 50 weight oil.
I put a new genuine gen2 oil pump in it when I did the 5S build. I have a later model pump sitting in he garage that flows more, though I think I'll leave it for now and only install it the next time that I have everything apart.

OK. That makes a lot of sense. I've heard they can get too much to the valve gear if cam journals are worn as yours were? I personally prefer a good healthy supply going up there to carry heat away from exhaust valve stems, ports etc.
Bit of a comparison but I haven't done hard driving like you.  Using Penrite 10 tenths 10-40.
Hot 95 degrees - 1000 RPM - 28 PSI.
                        -2000 RPM - 46 PSI.
                        -3000 RPM - 68 PSI.
Cold 25 degrees -1200 RPM - 72 PSI.
This is a Gen 3.running on a Gen 3. ECU.  It has the standard oil cooler which seems to keep the oil within 10 degrees of the coolant temperature.  Track day at Mallala the oil temp went to about 97 degrees.  Oil temp sensor is immediately before main oil gallery.  This engine has just short of 10k km. since I fully reconditioned it so quite fresh.

I have an external cooler. Maybe that is why mine reads lower than yours? 
The block and head is also different, which may affect it.
I tried starting it cold, and the pressure was 50psi.

What I see aligns with what these guys are saying - http://www.mr2oc.com/61-3sgte-turbo/331054-what-should-oil-pressure-when-cold-when-hot-3sgte-2-139-a.html
What I had before was definitely a bit low. I'm confident that what I have now is OK.
Thanks!

I have good news to report. The Haltech ECU is now fully installed, and I have completely rewired everything that is rearward of the seats. I did this because the old ECU was in the boot, and I wanted to have the new ECU behind the passenger seat on the firewall. There was still a lot of original wiring that I didn't need (i.e. weight!), so that's another reason why I rewired it all.
I finished it today, and the car started fine, and everything works. I still have my skills 😁
I spent the first 10 years of my working life as an electronics technician.
It took longer than I expected, though that's OK because I took my time and didn't cut any corners at all. Everything is nicely heat shrinked and there is next to no possibility that a wire will ever break.
My next job is to install the Aim MXL dash. It should be pretty easy. I'm going to install some additional sensors to use with the dash. I have an additional oil pressure sensor which I will use with the dash so I can see a big flashing light if I lose pressure. I wasn't able to do that with the previous dash. The dash will also pick up everything that the Haltech sees too. It will be a good step up from what I had before. 
I still have to do the final wrapping on the loom, so I won't post any photos of the job until then.
I'm getting closer to bolting the new turbo on.... #happydays

That's great news. It will be interesting to see if there is much gain from the new ecu.  

Here are some recent progress photos.

Looking good Glen. You sure like the gold stuff. Do you consider it effective as a heat barrier?
Is second photo your original turbo? I see the igniter module has snuck into the boot. Do you still use the original
Denso coil or something better?  I like the instrument display.

Yes it is great as a heat reflector. If it's good enough for NASA then it's good enough for me. Yes that's my old turbo. I'm thinking of putting it into my ST205.
I use 100% stock ignition. I bought a new oem distributor a couple of years ago. I haven't found the limit of the ignition system yet. Apparently it is somewhere around 600Hp.

I may, or may not have ordered one of these babies :-)