Those are a few nice pointer to keep in the back of the head.
So far the single overheated once pretty bad but since then I have had no major "new" issues. Damaged head gasket maybe but I still have no oil in the coolant or the other way around. Just oil burning ( bad valve and valve adjusters ) and oil leak ( upper head gasket needs replacing at least ). I plan on doing a rebuild on both my MMMs since they both have issues that need me to pull the head anyway.
As for the stress on the cooling system. I have not had any issues yet with either MMMs. Temperature is sitting just past the second mark on the low end usually. Single needs a new thermostat so that reached to about half way which is not bad either. Macro also had a bad thermostat but that one was open all the time preventing from the engine even from warming up and the gauge never really even passed the first mark even in summer.
By comparing these 2 pick-ups with my ( now no longer mine ) 1993 saab 900S these MMMs cooling works really well in the heat. The 900S always had high temperature, even when I by-passed the AC fan and had that turn on with the main fan. Then again what do you want from that. The 900S was build in a land where the daily max temperature in summer is the daily average temperature here all year around.

Plans are still to put an electrical radiator fan in the Macro, already put a new alternator in that on, 75A instead of the 40-45 original.
But plans are still plans and life seems to be passing me by on a lot of things lately so shall see. the NO1 is keeping them both running, driving and passing inspections.
So far that at least has been going ok.