Should be something like 05 or similar.
Yes a 1970 US spec 280SL would have an 05 cam.
Mercedes still produce the contemporary Euro spec 02 cam, which should be exchangeable with the 05 cam, as they both use the same camshaft bearings.
I just did a study on this recently, as I may also replace the 05 cam in my 1970 US spec 280SL (manual). But I want the more aggressive Euro spec 02 cam instead of the 05, which was chosen for the US spec 280SL due to emission control legislation in the US.
You can get a complete kit with a new 02 cam and new cam bearings for around 1000 USD from Mercedes. I can find the part numbers, if you need them. Both carries 114 part numbers.
Cheers,
Christian