The specified tires in the NA 350SL owner's manual were 205/70 VR14 (with tubes!)

One source was Vredestein. C$391 each Tires

Problem I read is that the current tire speed ratings may not have existed in 1972. So in some jurisdiction they require tires that match the maximum speed of car.
Max speed for a 1972 350SL was 213kph (~132mph). But there was a Euro 350SL and a NA 350SL (which was really a 450SL) Top speed for 73 450SL was 202kph or 126mph. So H rated would be correct if it was possible to get authorities to believe there were two different 1972 350SLs!

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Graham
85 300D,72 350SL, 98 E320, Outback 2.5