Probably, sure. He had it completely apart, including the core support, radiator, all of it. He could have changed it then if he wished to. But he did mention that the diesel engine might run cool in cold weather. Hasn't been a big problem.
Interesting what you say about the radiator. The shop which did the Toyota diesel swap oin my Series 80 left the original radiator for the truck in place. (my Series 80 began life as a USA-spec gas engined Cruiser) The radiator cools too well. In winter I have to block it off so the engine will...
I'm happy with the performance of my Series 80 with the 1HD-T engine and automatic transmission in it. The fuel mileage is good, especially for a large heavy vehicle which is not aerodynamic. I think the swap using a Toyota diesel makes the most sense, but maybe the new compact Cummins engines...
I had a 1HD-T Toyota diesel installed in an 80 series I bought for the purpose- a nice, rust free Western truck. I've been driving it about 2-3 years and improving it as I go. I'm very happy with it.