The 4.5 was designed to run at 175-180 all day except it can get warmer in traffic.

As for the fan clutch, it's hydraulic. With age they can get weak. If you start running above the (212?) mark above 175 in traffic, you MIGHT need a new one. There are many other things that can cause hot running too (scaled radiator at this age is very, very possible)

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Back in the saddle - 1972 280SE 4.5