Blair,
I think it's the 79 C job. The BBB lists p/n 001 203 89 75, or optionally, 001 203 90 75. Both open at 78-80 C.
The 87 C 'stat is for winter use, I'd stay far away from that one. The '71 C 'stat may be for 3.5's, they open at 72-75 C.
George Davis
'69 280 SL Euro manual