As far as I know there is no 172M, but why not fly the default 172SP?
There is/was a Cessna 172M Skyhawk, Mees... ;)...!
Scroll to the bottom right-hand picture; a 1977 Cessna 172 M...>>>
http://en.wikipedia.org/wiki/Cessna_172Many of them come under the generic name "Skyhawk"...beautiful aeroplanes...

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The new 172SP will do the job admirably (I think it may have a fuel-injected engine, so no carburettor freezing problems)... 8-)...!
Paul...Cessna Enthusiast...

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P.S. I think that the letters after the Cessna type number, refer to the year/period of manufacture...

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