Just wanted to close the loop on this thread.
I replaced the radiator with another. (Donor vehicle was a 1982 FJ40 from KSA). After flushing / burping the system, I stress tested the vehicle; the engine was choked / rev'ed and ran for about 30 min and there was no / limited impact to the temperature. I checked the gauge and cross-checked using a laser thermo-gun. I did the same test with the older radiator, and within 25-30 min's the FJ45 was running very hot. I've saved the old radiator as I was told it can be re-cored. If anyone wants it, give me a shout.
I checked the intake / exhaust valves clearances. There were several valves that were too tight and 1/2 that were lose. Now everything is as per spec.
I also did a compression test, as recommended by
@mattressking . 5 cylinders were at 140 PSI and the 6th was as 143 PSI; so I dont think there are any issues / concerns there. Just to make sure I did the compression test correct, individually I cranked the vehicle, to a count of 5, repeated 3 times per cylinder. Ignition coil & fuel supply was discounted.
I have not taken the FJ45 for a long drive, cause its too cold, looking forward to spring.