Slant six swap HELP!

Good question.
I am going off what is his diagnosis. I have given him a systematic list of how I would diagnose and narrow down the cause or causes of overheating. He bought the 170 to have as a backup. I inquired so if that is the determination, to replace, that we would be ready to do it without surprises.
I haven’t seen the car in question, but when I do, I will assist him in diagnosing the root cause. Thanks to all of y’all for your input. Feel free to keep sharing as it is possible that it is one or more of these or even something else completely.

RustyRatRod said

What if, on the off chance, since it has not been diagnosed, if you install the other engine and it still overheats since you don;t know what the problem is? Essentially, since yall are not diagnosing it, you are just throwing parts at it. People rarely fix cars in that way.

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